Which is a strategic move to A) get people to view MS as friendly to open source, and B) get people yearning for Visual Studio. Without Visual Studio, .NET is kind of a pain in the ass to develop. Not as bad as Java without Eclipse, but not anywhere near simple enough to be productive with substandard editors. Visual Studio makes .NET. Mono is intended to introduce people to the features that .NET provides and entice them into trying it where it shines, in Visual Studio, which runs around $500 a copy, which only runs on Windows.

The strategy with Silverlight is to concede that the client tier is multi-platform, and try to sell back end servers and developer licences instead.

This doesn't completely fit MS's other initiatives, but one of the benefits of being that big is that MS can try lots of things at once - to bet on every horse in the race, so to speak.

Although it is great that they are funding Mono and distributing silverlight on other platforms, I hardly think this is for altruistic purposes. They have a history of strongly pushing people towards their OS and platform and then ending support for third party tools (e.g. IE on Mac). I think moving towards something utilizing the power of HTML 5 and Javascript is the way to go long term.