They've already stuck their foot in the water with their recent deal with Novell (who own the SuSE Linux distribution).
http://www.technewsworld.com/story/54088.html
http://www.computerworld.com/action/art ... c=hm_topic
Which is really too bad, in my opinion. 9 years ago, leaked documents showed that Microsoft considered Linux to be the major threat to their monopoly status, and was making plans to eliminate it as a problem, see: http://www.catb.org/~esr/halloween/halloween1.html
This was followed by 7 or 8 years of their quietly funding "independent research" which tried to slam Linux from every possible angle -- that it was slower, hard to use, insecure, that using it could get you sued, that it was bad in just about every possible way. http://www.catb.org/~esr/halloween/halloween6.html
I started using SuSE Linux at work three or four years ago, and switched to it at home not long after, and have been quite happy with it. I can't view Microsoft's involvement with them to be a good thing, and don't like the feeling of waiting for the other shoe to drop. Because I doubt that this is the end of their involvement. Vista isn't exactly flying off the shelves, so the timing is suspicious to begin with. What comes next?
The whole situation creeps me out, so I've already switched one of my 3 domestic systems over to another, non-commercial Linux, and will do so with the others if things get any weirder.
Anyway, there's my answer -- that's what Microsoft has done so far. What they do next, I can't tell you. They could buy out Novell, but I think it's not in their interest to -- Novell would have lost money last quarter, and it was only a lump sum payment by Microsoft that made them profitable, so they seem to be on the road to becoming a Microsoft puppet, if they aren't already. Puppet status is probably quite sufficient for their purposes. Since 98% of Linux is not written by companies like Novell, but rather by unpaid volunteers, Microsoft may be trying to alienate the people who make Linux, who may not enjoy doing all that work, only to see it line the pockets of Novell. Or perhaps Microsoft is hoping to give some pricey, commercial version of Linux dominance over the market, so that they no longer have to compete with a free product, something which has always given them nightmares.
Time will tell.