The place to share links to other SRDs and games with open licenses. Probably none of us are lawyers, so maybe doublecheck if you're going to use them.

The Fate system (Fate Core and Fate Accelerated specifically) by Evil Hat are under a Creative Commons license! Licensing information can be found here: https://www.faterpg.com/licensing/?from=fate-srd

The 24XX system by Jason Tocci is also under a Creative Commons license, with the SRD (and information) here: https://jasontocci.itch.io/24xx