Bert Freudenberg is the main developer of the OLPC Etoys activity glue code (the part that makes Etoys behave as a proper Sugar activity). Etoys was the first official non-Python activity, developing it made him intimately acquainted with "sugarization" which he documented as the Low-level Activity API.
Based in Magdeburg, Germany, Bert is a long-time Squeak hacker, he worked on the Squeak Linux VM, wrote the Squeak Browser Plugin for Linux (his initial Sugar port used a similar approach), and built a Cairo-based Squeak rendering engine, to name a few OLPC-relevant things. Also had some previous Python experience (worked in the PyPy project) which helped in reverse-engineering Sugar.
As a freelancing developer Dr. Bert Freudenberg is available for contracting.