I'm doing software development professionally and as a hobby for over 30 years now. And OpenSource software for almost as long, hence a a lot of my stuff can be found on the Interwebs, e.g. on GitHub.


ZeeZide / Freelance: Working on projects/products for ZeeZide GmbH, as well as doing freelance work. If you got some interesting project, feel free to contact me.
Timeframe: 2015-today
Technologies: SwiftUI, SwiftNIO, and more.

Undisclosed: Major car manufacturer. Owning/developing a Swift SDK for secure communication with a headunit over CarPlay protocols. Protoyping various car automation features.
Timeframe: Aug 2022-Dec 2023
Technologies: CarPlay, External Accessory framework, Network.fwk, Siri Intents, Apple Maps.

Undisclosed: Helped a startup implement an iOS Network Extension, including a Network.framework based HTTP proxy.
Timeframe: Nov 2021
Technologies: Network Extension, Network.fwk, http_parser, SQLite.

Undisclosed: Major car manufacturer. Implemented a Swift SDK for secure communication with a headunit over CarPlay protocols.
Timeframe: Sep/Oct 2021
Technologies: CarPlay, External Accessory framework, Network.fwk.

Past for iChat.app: Simple but fancy viewer for iChat chat log files on macOS Big Sur. Written in SwiftUI.
Timeframe: 2021
Technologies: SwiftUI, QuickLook, Swift.

Battery Status for HomeMatic.app: Simple iPhone app reporting on the battery of HomeMatic home automation devices.
Timeframe: 2021
Technologies: SwiftUI, HomeMatic, Swift.

Shrugs.app: A native macOS client for the Slack messaging service. Written in Swift, using UXKit/AppKit.
Timeframe: 2018-today
Technologies: Slack API, AppKit, UXKit, Swift.

HMScriptEditor: A macOS app for testing and running HomeMatic scripts.
Timeframe: Q4 2018, Nov 2021
Technologies: HomeMatic, AppKit, SwiftUI.

Undisclosed: Helped a tech startup to implement a roaming solution, primarily working on the iOS SDK and the iOS application parts. Server side Swift running on the client, yay!
Timeframe: 2016-2018
Technologies: Noze.io, Swift, UIKit

Apple/iCloud: CalDAV/CardDAV client for Microsoft Outlook, Chrome bookmarks syncing extension.
Timeframe: 2010-2013
Technologies: CalDAV, CardDAV, C, C++, SQLite, MAPI

Outlook plugin: I worked on building a MAPI message store provider for Microsoft Outlook which stores Outlook entities into GroupDAV / CalDAV / CardDAV capable WebDAV servers.
Well, ZideOne has ceased operations. Don't ask.
Timeframe: 2007-2009
Technologies: C, C++, SQLite, MAPI, GroupDAV, WebDAV, CalDAV

Chamber Management System: I design and lead the development of a web based management system for a chamber of pharmacists in Germany. The system is built in Java on top of OpenGroupware.org technology.
Timeframe: Nov 2007-Jul 2009
Technologies: OGo, Go, OpenOffice.org, Java

OpenGroupware.org: For SKYRIX Software AG I architect, implement and maintain extensions to the OGo groupware server. This includes work across all layers of OGo, from the application logic through protocol layers up to the web interface.
Timeframe: 1996-2008
Technologies: C, Objective-C, Linux, PostgreSQL, SOPE

SMS/MMS Platform: An enterprise scale SMS/MMS transaction and service platform which is in use by various large media customers, MNOs and SMEs. My primary work is on system reliability, mobile handset detection and on-the-fly MMS repurposing.
Timeframe: Feb 2006-Sep 2007
Technologies: MMS, SMIL, C, Objective-C, Java, Tomcat, Linux, PostgreSQL

PostgreSQL Cluster: To secure the data in a large scale deployment of electronic datarooms we configured a PostgreSQL warm standby replication cluster using the write ahead logging facility of the server. The datarooms are accessed using a set of Ruby on Rails web applications.
Timeframe: Apr-Aug 2007
Technologies: PostgreSQL, Ruby on Rails

Card Management System: For a large German trust center I architect and lead the development of a system to securely manage applications for qualified signature / encryption cards (health professional cards). Prototypes implemented in SOPE, later moved to Java/Go.
Timeframe: Feb 2004-Apr 2007
Technologies: Java, Jetty, Go, SOPE, HPC, Smartcards, OpenSSL, MySQL

Agenor: For a large French ministry I designed and led the development of a massively scalable groupware server. Designed to serve 60.000 ministry workers. The project kicked off the ScalableOGo OpenSource project which is currently being continued by Inverse.
Timeframe: 2004-2005
Technologies: C, Objective-C, PostgreSQL, GroupDAV, WebDAV, CalDAV

Instant OGo: Designed and implemented an administration web interface for various Linux services. A proprietary OGo component which is in use in the excellent Instant-OGo product.
Timeframe: 2003
Technologies: OGo, Objective-C, Linux, SOPE

SKYRiX Publisher: Enhanced the SKYRIX web application server (now OGo) with an enterprise content management system. Was in use at a large plant research institute to maintain thousands of documents in a structured way.
Timeframe: 2002
Technologies: OGo, Objective-C, SOPE, Content Management

OpenSource / Sparetime

Lighter.swift: A set of technologies applying code generation to access SQLite3 databases from Swift, e.g. in iOS applications or on the server. Like SwiftGen but for SQLite3. Super fast and fully typesafe.
Timeframe: Apr 2022
Technologies: SQLite, Swift Package plugins.

ViewController: An approach to deal with application/navigation state within SwiftUI applications. Present as you used to!
Timeframe: Apr 2022
Technologies: SwiftUI, MVC.

docc2html: Swift package to read DocC archives and a tool to export them as a static website.
Timeframe: Jul 2021
Technologies: DocC, Swift.

Mio: A macOS port of the Nio chat client for Matrix.
Timeframe: Mar 2021
Technologies: Matrix, SwiftUI, Swift.

NWHTTPProtocol: An HTTP protocol parser (aka NWProtocolFramer) for the Apple Network.framework, an implementation of the Transport Services API (taps) in Swift.
Timeframe: Oct 2020
Technologies: Network.framework, taps, http_parser, Swift.

5 GUIs: A tiny macOS SwiftUI app that can detect the GUI technologies used in other apps, i.e. whether they use Electron, AppKit, Catalyst, etc.
Timeframe: Oct 2020
Technologies: LLVM, SwiftUI

SwiftBlocksUI: Slack can be enhanced with interactive dialogs and dynamic messages. Buttons, Pickers, TextFields and more. SwiftBlocksUI is SwiftUI for Slack applications.
Timeframe: July 2020
Technologies: Slack API, SwiftUI, Swift.

Direct to SwiftUI: An adaption of an old WebObjects technology called Direct to Web for SwiftUI. Instant CRUD apps, configurable using a declarative rule system, yet fully integrated with SwiftUI.
Timeframe: August 2019
Technologies: SwiftUI, Swift, DirectToWeb.

SwiftUIRules: SwiftUIRules adds a declarative rule system to the SwiftUI Environment feature. Think: Cascading Style Sheets or Direct to Web for SwiftUI.
Timeframe: August 2019
Technologies: SwiftUI, Swift, DirectToWeb.

SwiftWebUI: At WWDC 2019 Apple announced SwiftUI. SwiftWebUI is bringing that to the Web ✔️: The missing ☑️.
Timeframe: June 2019
Technologies: SwiftUI, Swift NIO, Swift

SwiftPM Catalog.app: A macOS frontend to the Swift Package Index.
Timeframe: Q4 2018
Technologies: SwiftPM, AppKit, UXKit, Swift.

SwiftObjects: An experiment to figure out how the WebObjects API might look like in Swift. Also: An Introduction to WebObjects, in Swift.
Timeframe: June 2018
Technologies: WebObjects, Swift NIO, Swift

SwiftyLinkerKit: This is an easy way to work with LinkerKit components in Swift. Includes SwiftyTM1637, a driver for the TM1637 7-segment chip, as well as an IRC LinkerKit chat bot.
Timeframe: Jun 2018
Technologies: LinkerKit, SwiftyGPIO, Raspberry Pi, Swift

swift-nio-irc: SwiftNIO IRC is a Internet Relay Chat (IRC) protocol implementation for Swift NIO, a basis for building your own IRC servers, clients and bots, a sample IRC server (including a web client), as well as some IRC bots, written in the Swift programming language.
Timeframe: 2018-today
Technologies: Swift NIO, IRC, Swift, WebSockets

swift-nio-redisRedi/S: Includes a RESP protocol implementation for Swift NIO, a convenient Redis client library for Swift, and a fast Redis server written in Swift: Redi/S.
Timeframe: 2018-today
Technologies: Swift NIO, Redis, Swift

µExpress: A tiny but useful Express-like web framework built upon Swift NIO, the new async-IO Swift framework by Apple. Popular blogpost in which we build µExpress: A µTutorial on Swift NIO.
Timeframe: 2018-today
Technologies: Swift NIO, Swift

SwiftXcode: Use Swift Package Manager directly within in Xcode. Ready-to-go Xcode templates for iOS apps, macOS tools, SwiftNIO and Kitura. No more swift package generate-xcodeproj!
Timeframe: 2018-today
Technologies: Xcode, Swift Package Manager

PL/Swift: Custom SQL functions and types for the PostgreSQL database server, written in the Swift programming language. That is what PL/Swift does.
Timeframe: 2018-today
Technologies: PostgreSQL Extensions, Swift

UXKit: Write code that works on both, UIKit and AppKit. Not only useful for deployment to macOS, but during development, reduce simulator/device testing annoyances. Drives CodeCows / ASCII Cows.
Timeframe: 2017-today
Technologies: UIKit, AppKit, Swift

Swift Server Project HTTP APIs: Wrote a GCD based, asynchronous implementation of the proposed, official Swift Server API. Maybe this gets pulled, maybe not. Probably not :-)
Timeframe: 2017
Technologies: GCD, Swift

ApacheExpress: mod_swift on steroids. Host Swift within Apache, that is, reliably :-) Stay tuned, a preview is available, but something bigger is in the works.
Timeframe: 2017-today
Technologies: Swift, Apache, mod_dbd

VueXcode: Want to edit Vue components in Xcode, but they just show up in black&white? Trying to change the file type using the 'Type' popup, but Xcode can't remember? Use VueXcode.
Timeframe: 2017
Technologies: Swift, Vue.js AppKit, Xcode, Cocoa

ZeeQL: Standalone Swift ORM / database access library primarily inspired by EOF, and in consequence CoreData, adding some ActiveRecord concepts. Can be used on Swift server, mobile or desktop.
Timeframe: 2017-today
Technologies: Swift, EOF, CoreData, SQLite3, PostgreSQL, mod_dbd

dockSwiftOnARM: Docker images for the Swift programming language that work on ARM platforms, specifically the RaspberryPi. Including Server Side Swift via mod_swift.
Timeframe: 2017-today
Technologies: Swift, Docker, RaspberryPi

mod_swift: A toolkit to write native Apache modules in Swift. Includes a subset of the Connect/Express framework of Noze.io which makes it very easy to write modules. Instead of reinventing the HTTP server, hook into something that just works and is battle proven.
Timeframe: 2017-today
Technologies: Swift, Apache, JSON, HTTP

Noze.io: The "Server Side Swift aS a Service" toolkit 😉 Noze.io are Node.js-like, evented I/O streams for Swift. Implements core Node modules like leftpad, net or http, as well as some external ones, like Connect and Express.
Timeframe: 2015-2017
Technologies: Swift, GCD, JSON, HTTP, Streaming

SwiftSockets, SwiftyHTTP, SwiftyExpat: SwiftSockets is kind of a demo on how to integrate Swift with raw C APIs. More for stealing Swift coding ideas than for actually using the code in a real world project. It also comes with a great Echo daemon as a demo, it's always there if you need a chat.
Timeframe: 2014-2016
Technologies: Swift, GCD, Expat, XML, HTTP

Go: Go is a set of Java frameworks to build powerful Ajax, web and web service applications. Comes with a lot of WebObjects compatibility as well as support for Zope concepts.
Timeframe: 2005-2010, 2014-today
Technologies: Java, Tomcat, Jetty, Eclipse, JDBC, HTML, WebObjects, Zope

ScalableOGo: A groupware server designed for massive scalability. The result of the Agenor project. This is a completely stateless application with a novel storage concept which allows high scalability despite using a RDBMS storage backend. For 60.000+ users.
Timeframe: 2004-2009
Technologies: GroupDAV, PostgreSQL, SOPE, Objective-C

GroupDAV: During a KDE/OGo meeting we designed a new groupware protocol to allow the lots of OpenSource groupware servers to connect to OpenSource groupware clients.
Timeframe: Dec 2004-2009
Technologies: WebDAV, iCalendar, vCard, Calendaring

OpenGroupware.org: I'm the project lead of OGo and coordinate the small but excellent community. Doing talks on various events. Currently working on the Java port of OGo, OGo/J.
Timeframe: 1996-2009
Technologies: C, Objective-C, Linux, PostgreSQL, SOPE

SOPE: Initially a clone of the WebObjects 4.5.1 web application framework, SOPE was enhanced with concepts from the modern Zope environment. SOPE is the application server used by OGo as well as SOGo. Includes a large collection of modules: XML parsers, iCalendar/vCard processing, NIO streams, EOControl, MIME/IMAP4 support, LDAP wrappers, database drivers, the appserver itself, etc
Timeframe: 1996-2009
Technologies: Objective-C, HTML, WebObjects, Zope, Database C Libraries, MIME, IMAP4, LDAP, EOF, XML-RPC, SOAP, SAX, DOM

Remote iTunes: Prototyped a small application to use the Nokia 770 as a remote control for iTunes running on an iMac.
Timeframe: 2005
Technologies: Maemo, Linux, AppleEvents, Cocoa, Objective-C

libFoundation: A clone of the OpenStep Foundation library, similar to gnustep-base. Initially developed by Ovidiu Predescu and friends. Took over maintenance around 2000. Worked on adding support for garbage collection.
Timeframe: 1996-2009
Technologies: GCC, Objective-C, Boehm-GC

GNUstep: Worked on various GNUstep subprojects. Improved the gnustep-make library, assisted the creation of the GSWeb framework, enhanced the GNUstep database library with additional adaptors and features. Bugfixes in the base library.
Timeframe: 1996-2009
Technologies: GCC, Objective-C, Make

libobjc: Designed and assisted implementation of garbage collection support for GNU Objective-C in cooperation with Ovidiu.
Timeframe: 1997
Technologies: C, ObjC Runtime, GCC

GTKKit: Implemented an Objective-C wrapper around the GNOME gtk+ GUI library. Modelled after AppKit where possible, integrated NSRunLoop with the X11/GDK event handling.
Timeframe: 1998
Technologies: C, gtk+, X-Windows

Apache ObjC: An Apache module to enhance the server with regular Objective-C NSBundle packages.
Technologies: Apache API, C, ObjC runtime

NGPython: Wrote an Objective-C / Python bridge for use in the Skyrix 3 web application server. Full support for Java-Bridge like 'jobs' files and a Pythonic API to Objective-C.
Timeframe: 1998-2000
Technologies: CPython Embedding, ObjC runtime

NGJavaScript: Wrote an Objective-C / JavaScript bridge for use in the form engine of the Skyrix 4 server. Allowed users to write small applications using HTML and JavaScript inside the groupware system.
Timeframe: 2000-2003
Technologies: C, ObjC Runtime, Mozilla SpiderMonkey

mod_ngobjweb: A non-streaming Apache module to forward HTTP requests to backend application servers. Capable to distribute requests across cluster nodes with a central registry daemon (snsd). Support for sessions stored in volatile memory. Now part of SOPE.
Timeframe: 1996-2009
Technologies: C, Apache 1/2 API

CocOOo: Small AppKit application to view OOo files. Loads the XML stored in the OOo file, transforms it into HTML which is then displayed in a WebKit view.
Timeframe: 2003
Technologies: AppKit, WebKit, OpenDocument Format, XSLT, Objective-C