i was wondering about gaming and linux, mostly about BF2
i am pretty sure that you can play the game on a linux system but can you play on the servers that are running on windows. without this there would only be a few servers that probably wont be ranked...

I can only give general advice since I have no idea what BF2 is. Gaming on linux can be kind of tricky, since most games you'll find are made for windows and won't work directly in linux. You can use programs like wine or cedega to trick the game into thinking it's running in windows, but this doesn't always work. If you take a look at their websites it will list programs that are known to work, but there might be things that work and aren't listed. Cedega is directed specifically for running games, but it also has a subscription fee to work. If you can get BF2 to work in linux, either with some emulator, or if it's available natively than I don't think it should be a problem connecting to a server no matter what OS the server is running but I can't honestly say I know much about that.

Yes - most games that have linux and Windows clients and servers are interchangeable.

I don't know about BF2, but Quake2 and I believe Quake3 and Half Life had a Linux download, so if you had the windows version, you could download the Linux software.

I'm assuming Battlefield 2 will only run under Wine or Cedega in which case it won't matter what OS the server is running. I honestly can't think of a game where server OS does matter but I'm sure there is some quirky code out there somewhere to prove me wrong

whether or not you are using an emulator like wine or cedega it shouldnt matter at all what type of server it is. You still interface the same way. Best way to find out would be to try it though.