rdonoghue, Conversation earlier today has me thinking a bit about the distinction between open and open source in RPGs (setting aside the topic of not-really-open RPGs).
There are plenty of open systems (that is, systems you can legitimately take and do whatever the heck you want with them) but a much smaller set of open source systems ( @malin keeps a nice list of them here - https://ttrpgs.com/post/foss_list - if you’re curious.)
It's a curious distinction.