I think Aaron Mattes came up with AIS, and then somebody else also came out with a book on AIS, which I think is when Aaron Mattes started calling it AIS: the Mattes Method.
I don't know about the whole patenting thing, but there are AIS CEUs that are taught.
So far, I am enjoying AIS much more than PNF. I have been looking all over for comparisons (adv/disadv) btwn AIS and PNF, but I haven't been able to find a thing.
Subjectively, it feels like AIS stretches the fascia moreso than PNF or static stretching. I've been looking more into stretching the fascia lately, so I'll update when I learn more.
It seems like one of the advantages of PNF is that it can strengthen end ROM, but Aaron Mattes also has an Active Isolated Strengthening protocol. I don't really know what the AIStrengthening entails yet though.
It is likely that I will start shadowing a physiatrist who uses a lot of AIS with his patients. The instructors at a recent AIS seminar I took at my massage therapy school said that they use about 80% AIS and 20% massage therapy in their practices, so there must be a lot more therapeutic and timely benefit from stretching than is generally recognized.