Perhaps you could keep this hosting service free by the use of advertisements or something else? Your hosting service being free for everyone would put it in the greenlight imo.
If all free slots become full, I will only accept premium users, and kick out free users who don't use their server much. That will make room for more premium ones.
Essentially, paid users have a higher priority for having an account than free users.
Blockland itself doesn't advertise. My hosting service makes up about 0.06% of Blockland's culture. I don't think advertisements would even help if I was hosting Team Fortress 2 or Minecraft game servers.
Blockland needs at least 600,000 players for HamHost advertising to even attract 1 premium user every month.