We've been laundering licenses on code on Stack Overflow and the rest of the SE network (whatever to CC (which can then be GPL'ed)) for a decade now. Consider

We've been laundering licenses on code on Stack Overflow and the rest of the SE network (whatever to CC (which can then be GPL'ed)) for a decade now. Consider https://softwareengineering.stackexchange.com/questions/269553/what-is-this-lisp-dialect-used-in-gcc-internals https://softwareengineering.stackexchange.com/questions/2695... The source code is GPL'ed, but that page is CC BY-SA 3.0. It's also fairly easy to assume that a fair bit of material on SO that was copied from employer's codebases into SO (and thus now CC) can be included in GPL code now too.