With iD software changing their Pro account server invite rules, where it used to be to 3 standard accounts invites per server and now changed to 3 standards accounts invites per Pro account (which means with 2 Pro accounts on one server, they can invite 3 standard players each = 6 standard players), we modified rules a bit to reflect this change and not to be confusing as much.
Quakelive subscription requirements for matches:
Read inside for updated rules.
1. The team's match lineup consists of players that have at least a premium subscription.
2. The team's match lineup consists of at least one player with a pro account, while rest of the players can be with standard accounts (+1 Premium/Pro for 5v5 cups).
Any team that starts a match without fulfilling these requirements will be sanctioned with a red card and a default loss. If a cup supervisor requests access to the server for streamers with premium subscription or higher, then the server spawner must allow them access to the server.
ClanBase admins will be able to spawn servers upon request but will NOT invite, which means that teams with standard users in the match lineup will not be able to play on CB servers.
Also found in Rules - Client Settings