1) You do not. You just download the program, install it, follow the instructions on the ^mumble link, and then join. You can also get it on a smartphone with an app, if you like! (You also do not have to have a microphone, as you can type to the other mumblers, and the program will read out your words to us!)
2) Mumble is super safe, as long as you're on the Famcraft channel
All the same rules apply to Mumble that apply to Famcraft. No swearing, no fighting, no religion/politics/etc. It's all clean fun
3) What Gedude said is probably the best idea. If Anna's spamming ^Mumble, chances are there are quite a few people on
4) You do not need an account. Just write your in-game-name into the nickname/username box, and log in