While redoing Terra Mutant, I realized the structure of Risus helped define certain concepts I want to see in-world that otherwise would not have even been addressed in a systemless setting. Something similar with The Devil Is and Sins and Paths occurred to me.
I do now realize the structure is in fact needed. Nothing prevents
the worlds use with another game system, but something is missing for
me in the world if it is systemless, perhaps because they were not originally systemless.
I think it might be that some concepts that are integral to a game world are nothing more than a suggestion, or an essay on a theme (such as Sins), when it has no mechanical reinforcement. As John Wick said to me once, "if it's a thing, have a game mechanic for it". In review of Terra Mutant, I started to feel it in the technology section, but it came home in the mutation section. In this case, almost a reverse of the Sin issue.
In this case, it was a situation where I was outlining very specific things that occur in this game world - specific mutations - but any Post Apocalyptic game setting that has mutants, will already have lists of mutations, and specifics of how they are used, so this isn't actually useful. It's a lot of insinuation of game mechanics, without the actual mechanics, for a specific style of play. It in fact, makes Terra Mutant useless as a systemless game world.
So...I guess I'm back to Risus, if only because it provides the very lightest of frame works to hang a setting on.
That being said, as I 'up' the production value, I will re-release the settings (all 17, yikes!) one at a time.
Apologies for the inconvenience.