Urbit's system creates an elite: the galaxy owners. They will, of course, use their positions to seek rent and grab "land" (control over territory, where territory is just planets and the like).
Somebody's got to own the resources, because they come from the physical world. That will be either power users who know enough about ownership, community groups, or commercial groups. Unless you have a fully distributed system with no centralised nodes, that's what you get.
Urbit doesn't seem to tie the ownership to physical scarcity of computing resources, though. They just invented some "land" to seek rents from, or sell to those who would seek rents. I'm all for spending money to bring physical computing resources to the system, including reselling access to those resources to others for profit, but the whole "stars / planets" false scarcity model ruins Urbit for me.