It's a bit of a mess. The implementation of a codec, that is, and encoder or a decoder can be open source, despite the format itself not being open. H265 does have open implementation, but the format itself is not open. The opposite can be true as well, there are proprietary encoders to open formats for example. Actual list of open video formats: https://en.wikipedia.org/wiki/List_of_open_file_formats#Vide...
What OP meant is that they would like an open format on the website, which, then, can be viewed in any modern browser. I think that caniuse is a good resource in this regard.
This is exactly why I am not convinced that VVC is going to be useful; seems to have little advantage over AV1, as well as being late to the party in the first place.
Well yeah, they wanna rent, so they have to develop these things. It also depends on what business deals they make in the background. If the format is secured in some applications, that might cement it as a quasi-standard, which then they can leverage for further popularity.
I hope open standards keep winning. Overall, everyone wins with the infrastructure being openly accessible, especially the common folk.