I'm trying to install the source code, but I already have python installed. I have python 3.3.3, and I'll probably update because I think that's slightly out of date. Is 2.7 required? I know there were a lot of changes in version 3, will the code still work?
Honestly, it's a little weird that Tuxemon is using 2.7. Support was dropped for it over 5 years ago, most major libraries have been Python3.x compatible for years.
Afaik the development Branche does work in Python 3 but the master branch did not (I tried it myself just a few days ago)
Yes, generally its better to use the development branch. Some platforms don't have python3 (android, maybe?) so I don't see us dropping 2.7 support, at least on the game client.