RetroZilla is my fork of Gecko 1.8.1 for improved compatibility on the modern web, with Windows 95 and Windows NT 4.0 in mind. Right now, RetroZilla's rendering capabilities are pretty similar to Firefox 2.0's, but as RetroZilla progresses, so will its capabilities.
Right now, I am focusing on RetroZilla Suite, a build of SeaMonkey/Mozilla Suite, because the suite provides both a browser and an email client in one package, along with other utilities. As RetroZilla progresses, I may also provide builds of Firefox and Thunderbird. The Firefox code is already in the tree, and if there's popular demand, I will copy over the Thunderbird code for personal builds.
I currently do my builds on Windows 2000 SP4 with Visual Studio 6.0 and MozillaBuild 1.2. The builds will also most likely work on Windows XP/2003, and possibly Vista and above, but don't take my word on it.
WARNING: RetroZilla is NOT a secure browser, and is provided for entertainment purposes only. It is a build of a browser from 2007, and contains most security vulnerabilities found since then. I do not recommend using RetroZilla to do secure activities such as banking or shopping. The RetroZilla development team is not responsible for any stolen information or malware obtained while using our product. USE AT YOUR OWN RISK.