NS = Natural Selection, a half-life mod
CS = Counter-Strike, a game using the half-life engine
And yes, welcome to the Tremulous community. I'll just warn you that there are two things these forumers hate:
1. Suggestions / ideas
2. Anything comparing Tremulous to another game in any way, particularly NS and CS.
Venturing into either of those "forbidden zones" will get you such lovely flames as:
"how about you actually play tremulous before you suggest anything"
"LOL, overpowered."
"...And while you're at it, let's make rifles shoot nukes"
"already been suggested."
"How about instead of trying to make Tremulous exactly like NS, you just go get NS?"
"wow, CS has NOTHING to do with Tremulous."
But other than that, the forums are good. Just be ready for some unnecessarily harsh criticism when suggesting things.