Was the menu system in WordPress 3.0 inspired by WooNav? Of course. Everybody knows that.

Is the code in the menu system in WordPress 3.0 the same code that was in WooNav? Not at all. It was completely rewritten from the ground up. Pretty much nothing remains of the original WooNav codebase. The code, data structure and UI was all entirely redone.

John O'Nolan was being generous when he said 90% of the code was rewritten. I would say 99% of the code is more accurate. There might be some function names that are the same, but everything else (including the code in those functions) is completely new.

I'm not sure how lavish credit can be heaped on Woo for the contribution considering what they contributed ended up being rewritten to the point that it is an entirely new piece of code. I think they have received a sufficient amount of credit for inspiring the functionality. But they shouldn't get credit for the code, because it's not the same code anymore.