At the bottom of the linked article is the answer to your question, with links to more information.

tl;dr (obviously tl;dr): This format is very, very easy to implement despite the patent risk, simply by assuming that any device new enough to be considering including it will have already licensed the relevant patents.

The patents would only cover the implementation that comes with the hardware, not any other software implementation running on it. This means you'd have to use the hardware decoder APIs to decode images, which is less than ideal when you want fast, low latency decoding.

But suing the party doing the infringing would be much harder. They can't just go after Google/Apple/Microsoft because all they're including is a javascript interpreter. They'd have to sue thousands and thousands of sites, most of them for amounts no larger than 1000 dollars.