I would like to add this patch, but (Ubuntu 10.04):
/home/cxl/upp.src/uppsrc/Core/Mt.cpp: In member function ‘void Upp::Thread::Priority(int)’:
/home/cxl/upp.src/uppsrc/Core/Mt.cpp:255:12: error: ‘SCHED_IDLE’ was not declared in this scope
...I guess more work is needed to resolve all compatiblity issues.
It has to work with Debian since 5, FreeBSD, MacOSX.