It will be all DON'Ts aside from "make original content." And it will be nothing but an expanding list of DON'Ts.
They aren't Intellectual Property Lawyers. They don't know how to read their own EULA. They will err on the side of caution.
This is pretty much it.
But maybe something from Trek canon will help explain things.
I hope you guys know the TOS episode "The Naked Time". Quick overview:
"The Enterprise orbits the planet Psi 2000, a world that was much like Earth in its distant past, tasked to observe the planet's impending disintegration. Commander Spock and Lieutenant Junior Grade Joe Tormolen beam down in environmental suits to a frozen surface laboratory and investigate the horrific deaths of the lab's scientists. "
Nothing for a few decades. Then along gomes TNG and with it the episode "The Naked Now".
And here is where things is very interesting for Foundry Authors. If you know both of these episodes, you know how you can reference one thing and drawing parallels... without having to copy anything AND still being able to tell your own story!
On the bridge, Riker steps out from the turbolift towards Data at the science station. Riker wants some information and enlists the help of Data. He has a vague memory of reading something about a person fully clothed in a shower, relating to La Forge's find on the Tsiolkovsky. Data agrees to help Riker and commences an extensive library computer inquiry for Riker(...)
It is not impossible to have your own story. I trust in all of your being creative individuals who can make your own stories come to life.