APIs are not subject to patent protection.
In fact, the general understanding based on a lawsuit by Sega in the early 90s & an earlier lawsuit against Franklin by Apple in the late 70s or early 80s is that APIs are not subject to any form of IP protection, although Oracle and SCO have tried to claim that APIs are sometimes subject to copyright in the past decade.
Nothing in the Windows API implementations should qualify for patent protection, as far as I’m aware. (Maybe somebody knee-deep in the code has a different opinion.) This doesn’t necessarily mean that nothing there is patented: it merely means that such patents aren’t valid, and shouldn’t stand up in court. (Email, online banking, and doubly linked lists all have invalid patents associated with them that people just sort of ignore because getting them overturned would be expensive.)
What Microsoft has done isn’t to make the patents ‘open source’, but instead add their patents to a shared pool where corporations who add their own patents to the pool can waive license fees.
This is different from open source in that:
- it doesn’t apply to everyone — in fact, it doesn’t even apply to individual programmers
- it has a different kind of effect on derivative works
Patents are wildly different from copyright (the only IP domain that supports open source licenses proper) because patents are centrally verified and registered (while copyright registration is purely optional in all berne convention countries & acts merely to expedite lawsuits) & because derivative works need to demonstrate their novelty in a rigorous way (in theory).
Additionally, patents rarely or never have broad written licenses. I’m not a lawyer so it’s unclear to me whether or not such contracts *could* be used, but I have never seen a written license (like a EULA or a GPL) that waives patent licensing fees for people who behave in a particular way while restricting the use of a patent for people who use it in some other way. (Presumably contracts with terms like this get drafted and signed between corporations on a regular basis.)
Patents also have no concept of fair use. (Of course, if a patent is invalid, you can use it as much as you want & nobody will ever enforce it, because filing a lawsuit is a great way to get it struck down at great expense to the patent holder. Patent trolls like to merely send nastygrams asking people to pay a licensing fee.) Basically, if a patent is valid, using it without express permission is liable to get you sued, regardless of whether it’s for education or the public good or whatever.
There’s a patent mechanism in some countries (including the United States) that’s similar to putting a work into the public domain: you can submit an application, and then (whether or not that application is approved) decline to have it granted as a full patent. In theory, that prevents future patents that are too similar from being filed at all; in practice, it makes future patents that are too similar very easy to strike down. (Unlike with copyrights, doing this still costs a lot of money. And, it needs to be done initially: once a patent is granted, it’s yours for 20 years and you can’t put it in the commons.)
tl;dr: Microsoft donating patents is a meaningless PR stunt from the perspective of people who want better Windows emulation, targetted at people who don’t know how IP law works.
More interesting is the release of the MS-DOS source code as open source. We might see some of that migrate into FREEDOS or dosbox, and see the handful of DOS programs that don’t currently work well in emulation get fixed.