Difference Between GPD and GURPS?

How big is the difference between GURPS Prime Directive (GPD) and GURPS (and/or GURPS Space)? Would any Non Prime Directive GURPS be close enough to GPD for it to be useful to GPD players/GMs for house rules? Basically, we are trying to determine if nonPD GURPS threads should be moved from the General Forum to the Prime Directive forum.

There one and the same with a slim down ship combat system that is unique to PD if I understand right.

I'd say yes for the most part - most SF-related GURPS can be likely used in a GURPS Prime Directive (GPD) game. Use common sense, of course - if the discussion is about a fantasy-based version it should probably stay in General, but general mechanics should be OK here.

Yes, the 3 threads are GURPS Trek. I should have clarified that in my first post.