Eclipse is an IBM project. IBM files more patents in a year than EVERYONE else combined. No country, company, or person comes close. That being said, Microsoft doesn't go after those projects because IBM doesn't go after Microsoft. It's an unspoken agreement.
IBM is a fantastic company to have patents, they rarely go after anyone. When Amazon decided to start suing internet businesses for using "1 click" check out, IBM threatened to sue them on 9 different patents. Amazon withdrew their lawsuits and IBM did the same.
There have been a few open source projects to be closed down for patent infringement, but there are so many open source projects they just simply go under and no one notices. Since they don't sell the products you can't sue them for monetary gain, but you can force them to close the project.
Care to explain how open source movement has radically changed the software world? I'm a huge fan and I contribute to nearly 10 different projects, I represent my corporation on 2 open source projects. But I'd never say it's radically changed software. Surely the 10 different licenses out there that aren't compatible with one another hasn't radically changed the software world? Those licenses have only slowed down certain advancements and technologies and resulted in tons of legal threats. There are a number of successful projects but beyond them the term Open Source is horribly misused. Open source is great, but it is never truly open source with the licenses they have attached to these projects.