It used to scare me because it abused its market dominance in much the same way Google does and because its ultimate end goal is inevitably end user lock-in, which is something I want to avoid at all costs.

It's true that they have changed over the last couple of years and have adopted open source, etc., but it seems to me that this isn't really because they've become intrinsically "less evil" - it's just because the market has forced their hand, and they now have to choose between future irrelevance and not being evil now.

I am pretty confident that if they once again gain a powerful monopoly like they used to have, they'll abuse it just like they did the last time.

One way they could do that is to bait and switch on open source/linux versions of .NET.

I've looked at F# and it is a nice language, but I don't really want to do any OSS development on it unless Microsoft somehow convinces me with a license that handcuffs future Microsoft so that they won't be able to do that (e.g. GPL, assuming that would work. IANAL).

This is almost an aside, but you should take a look at some of the stuff that comes out of Microsoft Research. They employ some of the biggest names in Haskell (Simon Peyton Jones for one) and have done some really interesting and bleeding edge work.