This is correct, people may join at any time, however I think I am gonna cap the main factions pretty soon, I am in discussions with one other person at the moment, if you want to join that puts us to 9 or 10 I think depending on how things fall out. That is probably as much stress as I want to put on my processor at the moment.
To reiterate, you can join, but I think that is about the limit for main players, come up with a faction idea and don't claim any land that is already taken, then send me a PM.
For any others who want to join in, you can do so in a few ways:
1. Via RP in the debate thread or even make your own for other announcements, you can take on the role of private citizens, news networks, corporations, or even government officials with permission of the player running the government. Have a conversation, propose a treaty or ban on something, threaten sanctions or propose a shift in policy.
2. Write fiction, most of the empires only have general notes on origins, you could flesh those out with permission from the creator, or write your own story in the setting, perhaps I'll even steal ideas to use in future plot elements.
3. Answer a casting call, at various times I might create a small faction and want another player to do something with it, for instance the NZDL is annexing California in a month in game and has announced it to the world. Their attack plans are set but I have decided that California is ruled by a few factions of murderous warlords, they will join forces in an attempt to stave off their assault. Someone could take the role of the head warlord and give me some ideas about how they want to defend themselves, perhaps even appeal to other factions for aid.
I might create a pirate empire at some point and want a pirate king to tell me what they want done. Little things like this could be run by someone answering the casting call, it is unlikely to be a permanent gig, but could be fun anyway.