If code is released with no license, the correct assumption is you should not do anything with it, in my opinion.
Yes.
Are you allowed to remember it?
Yes.
Are you allowed to use similar patterns / naming conventions / algorithms when your are trying to solve your own unique problems?
…I hope so, or you won’t be much value to your employer.
That’s all an AI does. Same thing as you, it’s just more efficient (in some ways).