The web is full of pessimistic comments about Open Source at the soon to be Microsoft-owned Yahoo!. If you belong to the crowd of those looking for shelter, let me try to show why I believe there is a very slim chance that www.yahoo.com will 301 to default.aspx anytime soon. I'll start by stating loud and clear that if you even suspect the Yahoo! Open Source stance plays a role in this deal, a few more brain cycles might be in order. Consider how Microsoft is going to empty their pockets in buying Yahoo, as the 44B$ deal will make more than a significant dent in Redmond's bank account: going this far just to replace Yahoo!'s FreeBSD gear with Windows is something even Ballmer can't pull off in his sweatiest dreams.
What this deal does is marking a 180° turn in Redmond strategy: Microsoft is clearly struggling to find a spot in today's industry where software as such is getting less and less relevant. They know how late they are to the party, and they're desperate to find a clue on how to catch up and be a major player again. Whether they will succeed, that's an entirely different matter, but I'm sure they all realize they can't just stomp their feet and pretend they can make it without Open Source. Definitely not in the short term, most likely not even in a few years from now: their failed Hotmail
Linux FreeBSD (thanks Christian!) migrations must have thought a lesson and left a few scars. Hadoop contributors on the Yahoo! payroll have little to worry.
It might actually be worth noticing how the acquisition of Yahoo! could be the greatest opportunity for Microsoft to become a significant player in Open Source. Nevermind Steve Ballmer, I really don't believe there is anyone in Redmond who hates Open Source with a passion: the Open Source strategy of Microsoft has been insofar guided by obvious business considerations. If you're the biggest provider of shrink-wrapped proprietary software, you have be defensive about the competitive and disruptive Open Source proposition. If your strategy shifts to the online advertising business, then Open Source can be your best friend. In any case, and as the ultimate bottom line, it would be downright silly for Microsoft to command Yahoo! into steering their technology and turn their .so's in .dll's: I don't think there's many silly people in Redmond. We will probably see much more embrace, and much less extend.
Zimbra vs. Exchange is possibly the one and only issue on the table, as it might be a nice side effect for Microsoft to control (one of) their Exchange competitor(s). Having said that, (a) I don't see anything happening at a fast pace and (b) if Microsoft ever tries to crush Zimbra, that would be a fantastic opportunity for a new or existing player to come up with yet another Exchange alternative. To be honest, though, I believe that in the next few years most of the e-mail business will move online, so all that won't be much of an issue anymore. Not to mention that the Zimbra guys are probably perfectly happy already with the Yahoo! cheque, and there is little doubt their excellent staff will find a new and better venture anyways.
I'm not exactly throwing parties at the idea of Microsoft owning Yahoo, even though I think a serious alternative to Google might be worth a few struggles, but I don't think the sky is falling for Open Source if Microsoft even gets to raise their flag over Yahoo!'s HQ. Vigilant? Sure. Worried? Not from a big picture point of view. Pessimistic? Nope.