It's basically the same thing. The big Netscape rewrite was from the 4.x code to the 6.x branch; the 6.x branch was what was released as open source, and when the decision was made to build a UI that encompassed only the browser and not the mailnews code, the resulting application became Firefox.

Yes, but Netscape Navigator got rewrote to Mozilla who eventually turned to Firefox. So same thing -- I referred to his example by the (current) name of the rewritten product instead of the name of the name of the original product that got rewrote.