Just for clarity, that snippet is talking about the actual CP/M code from Digital Research, not CP/Mish...which is BSD licensed.
CP/M was a commercial product, now sort of abandonware. The last holder was Caldera/Lineo. See the bottom of the FAQ page on the "Unofficial CP/M" site: http://www.gaby.de/cpm/faq.html
Yup. As it stands, the license only allows that one site to distribute Digital Research code. That was almost certainly a mistake when drafting the license... but finding out who the current license holder is, and then locating someone willing to change it, is likely to be almost impossible.
The current limited CP/M license was granted in 2001 by a company which no longer exists [0]. Whatever their reasons for only granting those limited rights at the time, the current copyright holders may be willing to grant broader rights. But, I imagine working out who the current copyright holders are may be difficult, and they may not even know that they have rights that they legally could grant, or have any good understanding of what the rights are about.
According to [1], ownership of CP/M was transferred to DeviceLogics aka DR-DOS Inc along with DR-DOS. But DeviceLogics appears to have gone out of business, so it isn't clear who currently owns the CP/M copyrights.
Sure seems like USC and relevant treaties should have language about abandonware / unlicensable copyrights. If they're gone, the copyright should either land in the public domain or be auctioned off for creditors.
I'm curious why it's not fully Open Source. What's the point to holding back?