I'm pretty sure Reiche or Ford have said the source to SC1 is lost. Far as I understand the reason Ur-quan Masters was possible is that it was based on the 3DO version. We're very fortunate that the 3DO version happened, not only because it gave us the voices but it had a different publishing arrangement from the PC where they legally owned the source and were eventually able to release it.
There have been some fan attempts at SC1 remakes or strategy mods to UQM, but none finished.
Steam Workshop won't happen for SC2 either; it's the DOS version.