Novell has a lot of stuff they do which is propriatory, btw. They've done a lot of operating system work on Unix operating systems and on their own Network operating systems as well as their groupware stuff and edirectory stuff, all of which is huge.
You have to know the difference between copyrights and software patents before this sort of thing makes sense.
Copyrights are awarded automaticly when you make some sort of creation. You doodle on napkin at a bar.. that is automaticly copyrighted to you. You write a book or write some peice of software that is now owned by you and is protected by copyright.
So copyright is something that is given automaticly and it covers your work, what you produced.
Patents aren't like that. Patents cost a lot of money and time to get and they have to reviewed and approved by the government's patent office.
Patents give you a monopoly on a idea or proccess or concept. Only you can use that idea. For instance say I figure out a new way to build lawnmowers to make them more durable. Now anybody who uses that same idea, even if they never heard of me or my patent or seen any lawnmower I made, they are automaticly liable to me.
That's not the same as copyright. Say I make a nice new web browser, some company can come along and copy it and such as long as they don't use any of my code. However say I patented 'tabs' for instance then nobody else can use tabs in their browser or text editor or website or anything like that unless they pay me money first.
The tricky part is that with software patents it's nearly impossible to NOT violate patents. This is simply due to the nature of software. Read this for more details:
http://lpf.ai.mit.edu/Patents/patents.html
But just assume now that I am correct. Microsoft IS violating Novell's patents. Linux IS violating patents. Mozilla browser IS violating software patents. You can't avoid it. You can hire a thousand lawyers to review your code and it's still have a 70% chance of violating some patent somewere.
So big companies like Microsoft and IBM get as many patents as possible for everything possible. Then since they are violating each other's patents then they do patent exchanges.
This is how they work around the broken patent system.
Software patents are a big big threat against Linux and Free software. Since 90% of the programmers work for small and medium businesses or do it individually then it's impossible to afford the legal fees nessicary to protect yourself. So by doing this they are legitimizing patents to a certain extent and making it easier for MS to sue other developers, at least in theory.
So far Microsoft hasn't sued anybody yet. They only have used software patents as a threat to scare OEMs (Dell, HP, etc) enough that they don't sell Linux on desktop PCs (not so much anymore it seems like it) and they use software patents to make sure that their media and office formats remain incompatable with other software unless that software's developers are willing to play by Microsoft's rules (which generally means it can't be open source or gpl'd).