(IANAL)
I would assume basic copyright restrictions apply.

A work is copyrighted when it is fixed in tangible form, regardless of whether you put the little C thing on it or whatever. The only exception is if you specificaly say it is public domain.

So if there isn't anything to agree to, you can probably do pretty much anything with the code as long as you don't pass it on to someone else. Disasembling, reverse engineering, ridiculing in public, etc. are OK. Posting it on your own web site is not.

I haven't read the details of the case, but I'm assuming that the license terms that were violated weren't things that are covered by copyright, or Netscape would have nailed them for copyright violations. Probably what Netscape was objecting to was reverse engineering of some kind. Something that is legal under copyright but against the license terms.

I don't see any impact on GPL at all. You don't agree to GPL when you download or use or reverse engineer (which wouldn't, hopefully, be neccessary, although I've seen some source code that...) the product. You agree to the GPL when you are doing things that would be illegal if there were no license at all. If you say "I didn't read the license" for a GPL violation, you are admitting to violating copyright laws.