1) The website was made by ckknight and Kaelten from scratch. The LL tool was made by someone from darkblizz, we had to borrow it from them. They're also the ones that are making the AI. The error messages came directly from SC2, ;). There is a syntax checker somewhere, i'll see if I can find it again for you. However, MilkyWayEdit is going to include syntax checking, etc, in the very near future.
2) Not sure about the the race choosing, :|. Unfortunately, I don't think there are any native functions for player vision. If you look in-game, you automatically have vision of your allies. I think it may work this way. Of course, that'd be rather ridiculous, we'll have to look for more. However, our list is complete. You can do something like... Give the player Observers' or something, just for testing.
3) orly? What language is it in? MWE is in C#, I don't think we've gotten started on this yet. If you can help, you're more than welcome to. Ping me or nicoli_s on the IRC.
4) Well, mapster uses the Curse account database, so everyone with a Curse Account can post here.