Google provides a royalty-free patent license, which can be revoked.
https://github.com/ImageMagick/webp/blob/main/PATENTS
AOMedia has a "royalty-free patent licensing commitment from all AOMedia members", but that doesn't mean that AV1 users won't have to pay to license patents from non-members.
http://aomedia.org/press%20releases/the-alliance-for-open-me...