The best way to answer your first question about [SpA] is to quote our post on the [SpA] application page:
We’ve had a few applications in the past from people asking, say, to ‘join our clan’, or from guys who have generally just got the wrong end of the stick. First off, you should know that [SpA] isn’t a clan, it’s a community. People that wear the [SpA] tag are SpA members and can also be an admin on our TF2 servers and their job is basically to make server life and the SpA community life as fun and enjoyable as possible. So when you apply, you’re volunteering yourself to become a part of the SpA member team and to help us take on the challenge of keeping SpA a great place to hang out and play many games. All in all, [SpA] isn’t just a tag!
As for your second question, I'm not entirely sure. I've never seen(or maybe just can't remember) anyone openly jump in and say "I'm Muslim!" Thankfully though, we are international. SpecialAttack was at first a(and still is) a European-based gaming community; over the years it has grown all around the world. Growing throughout different parts of Europe, areas of Australia, the Americas and many different diverse areas. Hopefully you'll get to meet us all, we are all uniquely awesome!