They are compliant with MPEG patent licenses - they distribute source code you have to compile yourself and for non-commercial use.

If you build x264 or other open source implementation of h.264/h.265, and embed it for example in commercial video conferencing software/appliance, you have to pay patent licensing fees for that product.

It's also why Firefox downloads a blob from Cisco to handle MPEG-4 video - Cisco covers the licensing for distribution et al.

How much does Cisco pay (to MPEG?) for that?

If I understand correctly, around 10 million USD per year (according to https://www.mpegla.com/wp-content/uploads/avcweb.pdf that's the cap, and from what I've heard Cisco is selling enough actual products to hit that cap, so providing their software for free to everyone else doesn't cost them any extra in licensing fees, just hosting and such)

That is such a nice service. Benefits everyone and near-zero cost for them.

Why is Cisco being nice about it? (Besides why not?)

I don't recall the specific timing of the release, so this might not line up, and I have no inside knowledge, just public information.

Cisco has some products which use compressed video in a browser setting. It would be useful if all browsers supported a good codec. Individually downloaded codec plugins suck, because installing is iffy. Therefore, give something away which doesn't cost licensing money to make your existing licensed products more usable.

And get some good feels on the interwebs.

Because several years ago, there was a fight over mandatory to implement video codecs in WebRTC. It was VP8 vs H.264. The biggest thing VP8 had going for it was no royalty payments. Cisco wanted H.264 because all of their devices supported H.264 and none supported VP8 and they already paid the royalties. So Jonathan Rosenberg, then CTO of the division of Cisco that managed this part of the business arranged to have Cisco cover the royalty payments for anyone implementing the WebRTC standards.

That wasn't enough, and WebRTC requires both VP8 and H.264 as MTI codecs.

Because it forces their competitors (in the video conferencing business) to take similar costs.

Could firefox download x264 and compile it on-demand?

x264 is for encoding only.

They don't get away with it. The are two separate issues: the software copyright license and the H.264 patent license. x264 itself is licensed under the GPL:

http://www.videolan.org/developers/x264.html

But if you use an H.264 encoder or decoder in a country that recognizes software patents then you need to buy a patent license if your usage comes under the terms of the license:

https://www.mpegla.com/programs/avc-h-264/

Software patents are not valid everywhere, x264 is brought up by VideoLAN in France, where software patents don't apply like in the rest of the EU.

So if a company in france writes open source software that infringes on a US software patent, and a company in the US bundles that source code in a product, is the US company liable for damages?

Yes. The company distributing the work has to make sure it has licenses for any required parts.

Yes, that's exactly how it works, the US company is responsible for following the US laws.

They sort of half not apply in Sweden too.

What do you mean by half valid?

Software patents are valid only if part of a larger invention, the algorithm itself cannot be patented.

However, patent clerks have also from time to time registered algorithmic patents.