Correct. http://www.infoq.com/articles/java-dotnet-patents
But what isn't? Plenty of Rails is sitting atop JRuby and friends. Nothing is immune.
Don't get me wrong. I'm not a massive supporter of .NET (outside of XNA) by any means. My point is if legal issues are what you're looking for; you'll find them; everywhere. It's just all so ubiquitous it's simply not cause for concern.
Anything can be made to be seen as illegal from a certain perspective. Everyone is suing everyone else. Does that mean we all pack it up and go home?