Sierra was purchased by Vivendi which was later absorbed by Activision.
The result is that Activision likely owns the Copyright (no copyleft bullshit here, please don't ever use that word again) but nobody really knows the actual status of the intellectual property rights for the Outpost games.
Semi-related, the trademarks have expired and have not been renewed so it's safe to say that Activision has no interest in the IP.
