How do I pick one, though? I need to know the differences between each version before I can pick, or do I have to install each version in order to discover which one is right for me? :/
I'll pick for you: Slackware.
Just to correct Noel, other than BMK nothing in BlitzMax is dependent on GCC tools. It was early in development but I actually got the first version of BMK using Microsoft compiler tools with very little hassle.
That's going with the assumption that the developers here feel like rewriting your tools.
Iron Bob: This is a case of ambiguity. Darwin is not, in fact, based on UNIX source code, only in design (and even then not entirely the same).