I'm using a code snippet that is licensed ritchey permissive license 10 but the newest version of the license available is 12. Is it bad that I'm using an outdated license? Can I upgrade to the latest version like with GPL?
I found Versions 10 and 11 on this page, but I could not find V12 (does it exist?). The license language states "The material must entirely remain solely under this license." which seems to be a clear expression of intention of the licensor.
I personally find the license language unclear. You can also see the discussion points in this and adjacent threads. And none of the Ritchey licenses made it on the list of approved licenses by OSI. If I were in your position I would try to replace the code snippet in question by something which comes under a better license.
B.T.W: With GPL you cannot automatically upgrade to the latest version, that's only possible if the license says "or any later version”.