The article doesn’t say MS is threatening to sue. It says that Microsoft “warned Asian governments on Thursday they could face patent lawsuits for using the Linux operating system instead of its Windows software.” This belief by MS is predicated on their assertion that “Linux violates more than 228 patents, according to a recent report from a research group, Microsoft Chief Executive Steve Ballmer said at the company’s Asian Government Leaders Forum in Singapore.”
MS’s dog in this fight is that they have a market (and presumably, patents) to protect, and if they can use mob-style scare tactics to protect it, they will.
“It’d be a shame if your store burned down one night, sir. Perhaps you should pay us to protect it.”
Various flavours of Linux being offered quasi-commercially is a relatively recent development.
Microsoft has made vague rumbling sounds that some Open Source projects (like this one) violate MS’s IP rights. So they are making threatening “Don’t even think about it!” gestures.
No, you’re not really missing much, although it’s really more about intimidation than litigation.
SCO’s litigation would never have come this far without a lot of help from Redmond, as it is.