Ive been playing around with JK2Radiant for a couple of months now and I still dont understand what the difference is between the different Bsp's (the build thingy) can someone fill me in?

First, don't use JK2radiant. Its buggy. Use the JK2 editor from [url]www.qeradiant.com[/url]

And BSP handles turns the .map files into files that the game can understand. Simply, the different commands handle lighting and vis to a certain degree.

Theres a lot of GTK Radiants, which one should I use?

SOF2MAP, JK2Rad's BSP program, and the far superior Q3Map2 are command-line programs, that, as Echoman said, convert .map files into .bsp files. The main difference is that BSPs hold lots more data: lightmaps, vis information (what you can see from different places), portal data (where you can physically go), and other stuff.

I say that they're command-line programs, but you don't actually have to use the command line to access them. GtkRadiant has a menu that offers different options for what to build, depending on whether you're doing a test run, or a lighting test, etc.

Definitely go for GTKRadiant. It's a lot cheaper, but better. :p

Okay so I downloaded GtkRadiant-1.5.0-2005. When I loaded it up, i get these errors:

Well, that isn't entirely surprising- I recall GTKr 1.5 causing problems with Jedi Outcast/Academy in the past, but that was a while ago, back in the early days of its release. I would reccomend giving build 1.4 a try- It has its occasional problems, but it's been much more stable to my knowledge. (And it wouldn't hurt to make absolutely sure that whatever build you download is Raven-specific.) However, I'm no expert in this area outside of limited personal experience, so if the elders say anything to the contrary, you would do well to listen to them.

Good luck.

Release versions with even numbers are stable releases, those with odd numbers are betas. So, I would recommend 1.4 like Sparrowhawk said. And make sure you have decent video card drivers, not some generic windows drivers.