- They're now, or soon will be, the largest supporter of free infrastructure for open source projects on the planet (GitHub)
- They've open sourced a massive chunk of their (IMHO) best-in-class language runtimes and language implementations (C#, F#, VB.net) and design and develop new features in the open
- They've contributed more than 1700 changes to the Linux kernel that can easily be identified with a quick 'git log --grep'
- They're the first company to make a real attempt at an industrial strength alternative implementation of the Linux kernel. Linux was supposed to be about choice, remember?
- They've open sourced the core chunks of the evaluation engine used in Bing (BitFunnel)
- They're a platinum member of the Linux Foundation. In other words, they pay Torvalds salary
- They support Linux as a first class OS on Azure and make it cheaper than Windows
- They have one of the largest and most active GitHub organizations
- They've joined OIN and, ignoring the actual patents involved, have thus in the process made an implicit promise never to attack any core part of the Linux infrastructure in the future
What more do you want?