LÖVE

I have been planning to join in on the next ludum(lew-dum???) dare compo. in April. But one thing that I never really thought about concerning uploading. Is that on love2d.org there is a separate download for love2d for each major OS. So does this mean, that when I finish a game and upload it. I will have to get someone else to compile my game on there windows computer(I'm on a mac) and then ANOTHER person to compile it on a linux?

You could just provide the .love file and give a link to love2d.org for downloading the runtime. But I don't know if the rules specify that you need to have ready-made executables.

http://www.ludumdare.com/compo/rules/

Doesn't look like they will "disallow" just throwing the .love up there, but you are encouraged to keep the upload self-contained. I'd say your best bet is to just make the Windows build, and then just do Jasoco's suggestion for the other OSes. We are already used to the shaft.

Alternatively do what I see a lot of indie cross-platform games do. Provide one single ZIP file with all the files for all three OS'. A game.app package for OS X, a game.exe with all DLL's for Windows and the appropriate binaries for Linux. Though if you can get away with it, just upload the .love with a readme saying to install Löve, and place the disclaimer on the download page too.