What does it take to become a developer, What sorts of skills are in demand?
Depends on the department/role. System modding is a whole thing of its own. FLHook requires prior knowledge with object-oriented programming, as it's based loosely on C++. Story development requires writing experience, spreadsheets familiarity, and a ton of patience. PvP Balance and effects require .ini knowledge; effects and models require certain artistic skills. Generally we ask that applicants understand the structure of the team, agree to take prerogative to help train themselves as needed, stick around for a while, etc.. It's good for people to realize not only what to improve, but how to improve, as they're learning the skills needed for what they want to do.
Sorry that it's a very broad answer, it's a very broad question.