[soltakss]

What you want is the most open possible licence.

That way, if someone writes something for the shared world and then wants to make it available to other games, say Mongoose RQ, then they could use Mongoose's OGL for the RQ part and this licence for the shared world part with no problems.

What you don't want is for people to be unable to share the world with other games.

Why would people want to use RQM with the world? Because they might want to use rules from RQM or extracts from settings already covered by an OGL. So, someone using Legendary Abilties or RQ-style magic might want to use the OGL.

Should there be a problem with having multiple licences for a particular piece of work in a shared world? I doubt it and I'd hope there wouldn't be.

Perhaps you could have one licence covering the extra rules and another covering the setting.