Just so you understand it goes like this:
A. Microsoft is spreading patent FUD to try to point out that Linux costs money and may increase your company's liability.
(This is true, but it's also true for Windows since Windows violates patents also.)
The reason it's FUD is because Microsoft does this every year about this time for the past 3 or 4 years. They are being a bit more louder about it this year, but still they refuse to disclose the patent.
Also new this year you had the KSR vs Teleflex and the Microsoft vs. AT&T decisions by the supreme court that have a large-ish impact on software patents.
The KSR v. Teleflex changed how patents are judged on their 'non-trivial' nature making it much easier to defeat patents in courts.
Microsoft vs AT&T is more complicated and I don't understand all of it, but here is the run down:
Microsoft pays MP3 licensing fees to Fraunhofer IIS-A due to MP3-related patents that Fraunhoffer owns. However Fraunhoffer isn't the only company that has mp3-related patents.
Microsoft hasn't been paying these other people and they got busted exporting PCs out of the U.S. to non-software-patent-honoring countries. USA export laws say any goods exported are treated under the same patent laws as if they were sold here in this country.
Microsoft argued that since they didn't have Windows installed on the PC then shipping the software without the hardware, and hardware without the software, didn't violate software patents.
http://www.softwarefreedom.org/ Even wrote a letter during all this to the Supreme Court in support of Microsoft.
The supreme court agreed so Microsoft won. The Supreme court also pointed out that the validity of software patents in general is in question because they have never ruled on it.
With regards to patents the court system has a lot of control...
So software patents are weaker now (but still a threat). Microsoft's patents, in general, are not that good to begin with. Many are going to be weaker then the ones in the KSR case and Microsoft refuses to divulge the patents they own.
Plus Linux has OIN backing it up. So if you sue Linux users OIN automaticly sues you. It's a doomsday sort of device. And Linux developers, in general, are pretty decent at avoiding patents and working with other companies to resolv issues.
So it's all FUD.
B. Microsoft has to be very carefull on who they threaten.
It's not 1995 anymore; Linux is commonly used in the enterprise. It's replacing Unux and since it's open source and has lots of open source tools for it it's very flexible.
Most enterprise folks have lots and lots of different sorts of software and hardware. Mainframes, big Unix systems, SAP, Oracle, Windows, etc etc etc. Virtualy none of it is able to 'talk' to one another. But Linux now has widespread vendor support and most of it talks to Linux. So Linux makes great 'glue' to hold all these different sorts of computer systems together. Plus it's a very good server OS in it's own right.
So the people that Microsoft are threatening with software patents are people like the New York Stock Exchange. There are a lot of very large financial, banking, and lending institutions that are huge customers of Microsoft that are also huge customers of Linux systems and IBM and such. Large manufacturing companies and all sorts of stuff like that.
These are some of the biggest and most powerfull companies in the world right now. They make Microsoft a lot of money, and they basicly control the stock market.
Microsoft can't afford to, and definately does not want to, threaten these folks... Or even lots of smaller companies. They are royally put the hurt to MS if they wanted to. Microsoft wants to threaten Linux developers and distributers and scare people away from doing large-scale Linux installations to replace their software.
C. So this is were the Novell-Microsoft deal comes in.
Novell-Microsoft deal is good for Linux on the face of it. Novell was smart for doing it. HOWEVER Novell royally F-ed up because they got tricked into the patent agreement. Novell got greedy and probably thought people would think that Microsoft paying them 420 million dollars to use Linux would be cool.
So the Novell-Microsoft agreement does a wormy thing to work around GPLv2. GPLv2 has a _implied_ patent license, but doesn't come out and say it. But basicly you redestribute the software under the same terms which you got the software. And sort of added restrictions you try to place on the software, which you yourself did not have, is against the license. So normally placing a patent restriction on the software would be a copyright violation. (GPL uses copyrights to enforce it's limitations as does any other license)
So the wormy thing is they don't agree not to sue each other (this would effectively place additional restrictions on the GPL software) What they do do is that they agree that they won't sue each other's _customers_. In this way they were able to work around the GPLv2.
Most other companies in similar positions, like IBM or Sun, would simply say 'as long as your using this software we won't sue you', which would work for everybody, but Microsoft does not want to loose that FUD.
So now Microsoft just sells those vouchers or coupons or whatever to those larger enterprise users and thus they can continue their anti-Linux-PR campain without threatening dangerous people.
Since those big customers are now immune by the Novell-Microsoft agreement then Microsoft figures aren't going to give a crap anymore about MS threatening to sue everybody. They are probably right.
D. The GPLv3....
The GPLv3 is a attempt at modernizing the GPLv2 license. Since the GPlv2 was created software is much more international, GPL'd software is used in lots of unusual places, people are finding ways to worm around the license (tivo, Novell-Microsoft are two examples, but aren't the only ones), and all sorts of stuff like that.
One of the things that they are working on is to add patent language to it. The GPLv2 has implied patent language, but that is confusing, so GPLv3 wants to solidify it. Lots of other common open source licenses have patent language.. IBM public license, Sun's CDDL, Eclispe license, Mozilla public license, Apache license, etc. etc.
So this was ongoing before the whole Microsoft-Novell debacle. But GPLv3 drafts changed as a result of it.
So the goal now for the GPLv3 is that instead of making what Novell-Microsoft did illegal, they are making it so that any 'covenent not to sue' automaticly extends to other downstream users.
So that if I buy a copy of Suse I am protected from Microsoft. If I was to give you some code from that system then you would be protected also. So the 'coventent' automaticly extends with other legal uses of the GPLv3 software.
So this is very cool way of doing things. Now companies that do own patents, but what to use and redistribute their own versions of GPLv3 software can do so without having to give up control of those patents. They just have to enter into a 'convenent not to sue' themselves. This also is a more internationally-friendly way of doing things and avoids a lot of the pitfalls in different places with regards to differences in patent law.
Now it was assumed that when Novell started shipping GPLv3 software then Microsoft would just pull out of the agreement because they don't want to see their FUD go away and their agreed protections spread to other people.
But they _can't_. On the coupons they gave out there is no expiriation date. You can get the coupon now, wait till Novell starts shipping GPLv3 software and then buy that version. Then the 'covenent not to sue' will spread to other people.
Hope that makes sense.
I am not a lawyer and I don't know how valid all this reasoning is. Also I am probably making big mistakes on some parts of it, but I think I have the idea. It sounds fishy to me, but Even Moglen is a history of law professor at Columbia University so if anybody knows this stuff he does and this is mostly his (or my guess/interpretation of it) theory on it.
BTW on his homepage be sure to check out the "Die Gedanken Sind Frei: The Free Software Movement and The Struggle for Freedom of Thought" lecture he gave in 2004.
http://emoglen.law.columbia.edu/
It's very good.