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 Apache Subversion version control system for over a decade. I have also made contributions to APR, Apache HTTPD, and Apache 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