No it isn't "just as OLPC does". OLPC is providing software and hardware. By rights Microsoft's attempt should fail, but competition is rarely fair and free where Microsoft is involved (I don't want to say "IMHO" at this point because there is more than enough factual legal history for this statement).

What's worrying is that, if it gets traction over OLPC, developing countries will get the familiar MS lock-in, and with support for XP due to expire soon, what's going to happen with Vista? Will that also be $3? What do you think?

If you think companies wouldn't dare risk those sorts of tactics, I offer the (much more heinous) example of Nestlé, promoting and giving "free" baby milk out in developing countries in hospitals, which results in breastfeeding rates dropping. This leads to the WHO's statement that "WHO estimates that some 1.5 million children die each year because they are not adequately breastfed." and blaming unsafe bottle feeding, caused by both unclean water, and unaffordability of baby milk. It's off-topic, but if people are concerned about this issue, see http://www.ibfan.org/.

Anyway, the point is that large companies are perfectly capable of screwing those in developing countries under the pretence of charity. And amazingly they continue to get away with it.