Just retrain the model using properly licensed code? ("just" is doing a ton of heavy lifting, but let's be real, that's not impossibly hard)

There's not many licenses that let you reuse code without including the same headers / licensing blurb. You're in public domain, non-copyleft territory. WTFPL etc.

There is no such thing as properly licensed code because it is a function of the what is legally acceptable for your company and what it intends to do with the work.