Stefan Sperling

Software Development and Consulting

Based in Berlin, working anywhere in Europe


I develop software for businesses and non-profit organisations, drawing on experience as professional and volunteer contributor to various projects.


The OpenBSD project develops a UNIX-like general purpose operating system which is free, functional, and secure.

My areas of contribution include device drivers, IPv6, UTF-8 support, and wireless networking. I port existing software to OpenBSD and develop new OpenBSD-specific software such as Game of Trees.

Apache Software Foundation

The Apache Software Foundation (ASF) spans over 130 projects covering a wide range of frameworks and applications enjoying wide use within the industry.

I have been contributing to the widely-used Subversion version control system for over a decade. I have also made contributions to APR, HTTPD, and Serf.


Contributions to Osmocom, git, XFCE, Gnome, e17, Pulseaudio, Python, FreeBSD,, OTR, ...


New project proposals are always welcome! Whether you have a project that fits my existing skill set or will allow me to learn about new areas which I have not explored yet, do not hesitate to get in touch.

My existing clients include non-profit organisations, small and medium businesses, and research institutions. As such, I do not list one-size-fits-all consulting rates on this page. We will arrive at a fair and clear contractual agreement in writing before work on the project begins.

OpenBSD end-user support for setup, configuration, deployment, and maintenance is available on request. I provide hands-on training workshops about OpenBSD pf firewalls. My standard table of contents of detailed training exercises contained in a 2-day pf workshop can be viewed here. I will customise and expand my written training material to meet your requirements and will make all of it available to you under a CC-BY Creative Commons License.

Ich biete OpenBSD Schulung und Support auch auf Deutsch an.

Together with elego I offer support and consulting services for the Subversion version control system.


  • Professional Focus
    • Software development
    • Development process consulting and tool support
    • Workshops and training for developers and end users
  • Projects
    • Osmocom developer (2018 to present)
    • OpenBSD support (2015 to present)
    • OpenBSD developer (2008 to present)
    • Support and consulting services for Apache Subversion (2008 to present), with elego
    • Apache Subversion developer (2007 to present)

Download curriculum vitae


Stefan Sperling

I am fluent in English and German.

PGP: 8BC4 DAE0 C5A4 D65F 4044 0107 4F7D BAA9 9A59 B973