https://github.com/NVIDIAGameWorks/FaceWorks/blob/master/license.txt.
I don't know that a single person has actually posted yet the correct legal interpretation of this license. The source code here IS open source. The object code and art assets can be used, but not modified and redistributed in modified form. Object code = black boxes (.dlls, etc.). The object code + art assets are "open-ish" or whatever you want to call it. It's essentially free to use but not to change.
nVidia license said:
Source Code: Developer shall have the right to modify and create derivative works with the Source Code. Developer shall own any derivative works ("Derivatives") it creates to the Source Code, provided that Developer uses the Materials in accordance with the terms of this Agreement. Developer may distribute the Derivatives, provided that all NVIDIA copyright notices and trademarks are used properly and the Derivatives include the following statement: "This software contains source code provided by NVIDIA Corporation."
As long as you obey the formalities in the document, its open source. Plenty of open source licenses require you to include an attribution to the original author, this is nothing new.
The key thing is how much of the actual effect needs compiled source alone to run, and how much requires black boxed "object code." I haven't examined the repository in depth enough to say whether it is effectively closed or open source because this 100% depends on how much of the functional code is in source and how much is in object code.
BUT nVidia can cancel your license whenever they want. So, they can "un-open" the source as they please. They don't get to own what you built on top of the source, but you also can't use their source any more.
I would not put overly much stock in the cancellation clause. I haven't done the research so this is just speaking from my current knowledge, but I'm pretty sure there is no case directly on point for this sort of situation. Fair use (for copyright aspects), exhaustion of rights, laches, promissory estoppel, invalidity (for patent aspects) etc. all come into play (in the US). If you wanted to fight that cancellation you could easily have a case that wouldn't get thrown out and could stall that for years (or at least until the preliminary injunction, TRO hearing if you get really unlucky...). The reason people don't fight these is that in all likelihood you could raise infringement on all 4 IP families, and breach of contract, plus maybe even some tort stuff. It would be a massive battle for not much gain compared to refactoring the code.
It certainly isn't as straightforward as the MIT license, but its definitely more than the old GW black box method.
Even if you don't change the code (to avoid nvidia having any right to cancel any part of your game), you can still look at what code is running and optimize based on inspection of the actual source, which is still a huge leg up. (Unless the technique is patented and they decide to cancel the game, and that isn't estopped or precluded by (F)RAND doctrines.)
