Like kamelito already said: this stuff hasn't been leaked now, it's been leaked in the late nineties. Rumors have it that Tyschtschenko handed out the sources to a whole bunch of people in Germany (in addition to Phase5, which already had them) to make sure they don't get lost during the next bankruptcy.
These sources were all over the warez boards in 1997 or 1998.
It's the original 3.1 sources from Commodore, they require quite an exotic setup to compile (an obscure SunOS/Solaris based Cross-Compiler amongst other things, IIRC), Olaf Barthel had to spend quite a few hours to make them compile/assemble with modern tools before they could be used as the base for OS 3.5+.
Last edited by Korodny; 29 December 2015 at 18:29.