Nitpick: initially there was Netscape Communicator/Netscape 4 (https://en.wikipedia.org/wiki/Netscape_Communicator), which got open-sourced as Mozilla Suite when Netscape went out of business.

(Confusingly, there were many more versions of Netscape after 4, but Mozilla Suite didn't really derive from them. Netscape 6 and 7 were just contemporary versions of Mozilla Suite with some Netscape badging slapped on. Netscape 8 was based on early versions of Firefox, dropped the other non-browser "suite" components, and was only released for Windows. Netscape 9 was also a browser-only thing, but went back to being cross-platform.)