Of course, they can't do that, because the source technologies they've put together are themselves patent-encumbered. An AV-codec is a lot like a modern pop song: a piece of IP entirely made up of licensed samples of other people's IP.

I think a more subtle "open-sourcing" of this IP could still be possible, though. Maybe one that still requires that large corporate players that are going to sell their derivative products, acquire a license the traditional way (this is, after all, what the contributors to the codec's patent-pool and R&D efforts based their relative-R&D-labor-contribution negotiations around: that each contributor would end up paying for the devices of theirs that run the codec.)

Maybe there could be a foundation created under the stewardship of the patent-pool itself, which nominally pays the same per-seat/per-device licensing costs as every other member, but where this money doesn't come from revenue but rather is donated by those other members; and where this foundation then grants open-source projects an automatic but non-transferrable license to use the technology.

So, for example, a directly open-source project (e.g. ffmpeg) would be granted an automatic license (for its direct individual users); but that license wouldn't transfer to software that embeds it. Instead, other open-source software (e.g. Handbrake, youtube-dl, etc.) that embeds ffmpeg would acquire its own automatic license (and thus be its own line-item under the foundation); while closed-source software that embeds ffmpeg would be stuck needing a commercial license.

Is there already a scheme that works like this?