Not for code I just looked at. But if I find the MIT/BSD code useful enough that I want to have such a functionality in my program, I would just use the code an

Not for code I just looked at. But if I find the MIT/BSD code useful enough that I want to have such a functionality in my program, I would just use the code and give attribution as the license requires. In all the cases, where I not intend to include GPL code in my project, I consider it unethical and legally improper to look at it and then write my own version of such a functionality.