is there any plans to support this use case: offering repositories only to a set of nodes? I can imagine people wanting to collaborate in private but not wanting to be on Github.
Yes, these are what Radicle calls "private" repositories. They are invisible to the rest of the network, and only shared amongst trusted peers. Note that they are not encrypted at rest, which means they cannot be stored on intermediary nodes that are not part of the truste set.
