We currently provide binary packages for RPM and DEB based
GNU/Linux distributions. The sources should work on any Intel based GNU/Linux
without issues and they do work on SPARC/Solaris. Further the sources are 
ported to the IBM iSeries platform running Linux and are known to work on
various BSD platforms.
<br />
Most of the core libraries already work on MacOS X. To build a complete MacOSX
port we have started the
<a href="http://www.opengroupware.org/en/projects/macosx/">MacOSX porting project</a>.
<br />

Concerning Windows, check our <a href="http://www.opengroupware.org/en/about/mission.html">mission</a>
document. We are not actively working on it, but have it on the radar ;-)
<br />
Finally, the sources should compile without major issues on any Unix(tm)
like operating system which is able to host GCC and GNU make. If you managed
to build on your specific platform, please send us
<a href="mailto:feedback@opengroupware.org">feedback</a>.