Boo is a python-like language that is compiled by the CLR. This makes it exception for Empeld, since it can pretty much run at native-times.
You can read more about boo on their github wiki.
Read about Empeld's preprocessing: Bocce
In addition to the Code rules for gamedev, there are a few other tricks you should follow when writing in Boo.
Use declared types for performance-critical pieces
By default, boo lets you use weak-typed variables to compute against. eg:
def GetBlock(x, y, z): bla
This is nice to read, but because Boo can't tell what
z are, it has to guess, and that can be slow. So it can be MUCH faster if you specify it yourself.
def GetBlock(x as int, y as int, z as int) as IBlock: bla