Boo is also integrated in SharpDevelop [1] which is an IDE for the .NET framework. I used it because I did not want to spend an hour to install Visual Studio on my machine back then. When I look at the releases page the MSI install packages are around 15 MB, which is much smaller than Visual Studio was in mid-2000s.
[1] https://en.wikipedia.org/wiki/SharpDevelop [2] https://github.com/icsharpcode/SharpDevelop/releases