DEC OSF/1, Digital UNIX, Compaq Tru64, Compaq UNIX. Did I miss anything?
All of these are the same OS, Digital^WCompaq's proprietary UN*X for their alpha chip computers. It's all new code, with all new bugs. This means that experienced admins will have many problems, as they cannot rely as much on their experience to prevent problems.
Case in point: for a long while, you could crash any newly installed OSF/1 system by running a debugger (DBX or GDB). Eventually people started learning to install the right patch immediately on opening the box. (Today this has been fixed.)
Perhaps it's no wonder they keep on changing the name.
EMERGENCY UPDATE, stardate 20030201.16110782. This bit of space junk came up on the USS Ariels' scanners. Compaq is no more. Given their beloved HP-UX, presumably HP will kill their other UNIX. But... any chance of a name change operation before that?
EMERGENCY EMERGENCY UPDATE UPDATE, stardate 2004something. Nope, HP didn't kill Compaq Tru64. "HP Tru64 UNIX" appears frequently on their website. Welcome to your world.