Everything.
They are trying to gain some ground in the OSS world, so that they could influence markets that contribute to OSS development (like the server market where Linux is the preffered choice).
In case you didn’t notice, microsoft is not exactly “keen” on the whole concept of OSS. It’s their one ensuing threat that they are tying to get rid of.
Hence why I see this “deal” as another microsoft business trick.
I’ve felt for many years that Microsoft was making a mistake by “overlooking” Linux. It’s good to see that beginning to change, but alas, I see that there are still heads in that company who assume that “We must 0WN You.” And that, somehow, Novell possesses “something to own.”
The way to succeed in Linux-land is to make great products that people want to buy. You don’t actually have to release the source-code to them if you don’t want to. You just have to be able to run your stuff well on that system … and to interoperate with the myriad of different things that are there (most of which you do not 0WN and never will) … and “provide great products that people want to buy!”
Sometimes I think MS would have been a much better company, albeit a somewhat smaller one, if they never had an OS “monopoly.” Or, I should say, never thought they did.
You really don’t have to “RUL3” to W1N … 
Well said, Sundail.
Success is, after all, relative. I can become 10th in the Tour de France and still feel successful. I would, too.
I have only recently realised why too many possessions are bad. My philosophy is: you should own all the minimum requirements, plus some luxury you fancy most.
Microsoft is rich enough, Bill Gates especially. They really don’t need any more money. God, I hate Extremistic Capitalism.