Everything you mentioned but Vista is available in a free version precisely for things like the aforementioned weekend projects. And I don't think that it's any more fair (for 99% of users) to include buying an OS in "prerequisites for fun weekend project" than to include buying a computer in the first place.
countercounterpoint: They are available in a free version because Microsoft really wants you to build things for Windows. If they could give you the full versions for free without cutting off the air to the 3rd party tool vendors, they absolutely would:
I don't know if there's proof of whether they are available because of competitive pressures from the open source stack or from Oracle, IBM, etc., but I think we can all agree that competition is a good thing in general.
Still, my point is that while the open source stack is a smarter choice for many, many projects, between free versions of closed-source software and initiatives like Microsoft BizSpark, startup cost shouldn't really be the deciding factor.
