If you consider a platform cooperative to be a centralized and hosted system owned, operated, and governed by a cooperative, it is easy to tell what the cooperative owns.
If it's an open protocol, how does a cooperative own it?
A cooperative could form to create and maintain software that runs the protocol. SSB is starting more than one organization like that
Or cooperative could form to host sites that run the protocol, for example, social.coop. (part 1 of 2)
@bhaugen Capitalists centralising everything and always competing for profit rather than collaborating can never get cooperativism right. Free Software is anathema to their process, even if they benefit from it, there's a fundamental philosophical impossibility in being for capital and being for collaboration at the same time. US Liberals really need to make their minds up.
Sunbeam City is a Libertarian Socialist solarpunk instance. It is ran democratically by a cooperative of like-minded individuals.