Specifically? I'm trying to produce a CP/M clone distribution which is DSFG-enough to ship with emulators (and also to run on real hardware should people wish). The original Digital Research source has a nasty clause in it which, AFAICT accidentally, means it can't be redistributed, so I'm finding open source alternatives and bundling them together. What this is involving is trawling through the archives trying to find free or public domain pieces and piecing them together.
Example: the command shell I'm using (the CCP in CP/M terminology) is an enhanced command shell alternative called ZCPR. The first version of this, ZCPR1, which contains no copyright notice, and which was released in 1982 to the SIG/M public domain distribution group. I found the release announcement (
https://github.com/davidgiven/cpmish/blob/master/third_party/zcpr1/Announcement.pdf) which contains a passing reference to it being released into the public domain. Is this good enough?
I was lucky there in that I found the announcement; there's plenty of source which has nothing at all, not even a copyright notice. For example, everything I've seen printed in Dr. Dobbs' Journal...