Even if Screeps had one fixed plan, it would still be possible for anyone to launch "ally" programs on behalf of several users and thus get the same total CPU increase.
However, keep in mind, that Screeps is not about having many creeps but about controlling them properly. More CPU, more rooms, and more creeps often don't offer any advantage over another player if you can't manage all this.
The good thing about Screeps is that online users counter means nothing here. You could build a large empire with a complex network of roads, sourcing, mining, manufacturing, border defense which would live on its own, while you would occasionally drop in from time to time just to check the situation and polish your scripts, if needed.
Every MMO, regardless RPG or not, will require you to invest time to repeat some actions and pay attention to it as much often as you can. See Travian for example. Screeps will not, if you manage to write decent scripts.
This is where Screeps will be different. You will need to think hard how to adapt someone other's script for your landscape, game environment, creeps setup, etc.
Think of it as Starcraft with code editor panel in the bottom. Your script controls everything, but you can still click at your creeps to see their info and memory.
Every player will have CPU limit on how much time his script can use in milliseconds. So that's the challenge to make the AI strong and not exceed the resources.