Patent complications do seem to be a factor, but it's unclear if in practice it'd be "loads of money", as the project page suggests many existing systems already have licensed decoding capabilities.

Also, one of the patent pools covering HEVC announced in 2016 that software-only implementations would be royalty-free:

https://www.prnewswire.com/news-releases/hevc-advance-announ...

Whether still-other licenses from other patent-holders might be necessary for software-only, in-browser decoding is unfortunately murky.

Why? The "licensing" information at the bottom of the page makes it seem like it's open source?

Because it's based on HEVC. HEVC patents have a very complex (and expensive) licensing situation right now.

The author can only give up his own rights. Identifying and acquiring any patent rights owned by other people is up to you.

Open Source does mean it is free of patents.

Does not mean it is free of patents.

Oops, right. I really thought I wrote this. Sorry.

Yeah, I assumed it was just a typo, but I figured we wanted to be absolutely clear here.

I promise I will never become a lawyer or write math books.