Microsoft releases 1.25 and 2.0 versions of MS-DOS as open source

Sorry, I was talking about when I received the sources in order to join the MSX-DOS 2.50 project, in 2008. Certainly Git still wasn't mainstream by then, but Subversion was a thing - and in fact the first thing I did before touching these sources was to create a Subversion repository. And again, I can't envision any practical software development system based on sending around zip files.