Firefox Fork ESR - Extended Service Release
XUL-Based Web Browser XUL - XML User Language Interface
XUL Plugins Removed in Firefox 57 Replaced with WebExtension broke tons of legacy plugins like VimFX and Vimperator Basilisk doesn't support WebExtensions
Australis Firefox Interface - Firefox v29 - v56 NPAPI plugins - Flash, Unity, Java NPAPI - Netscape Plugin Application Programming Interface Disabled in in Firefox 52
Goanna rendering engine - Fork of Mozilla Gecko Pale Moon based on Firefox 38 ESR
Basically just a development branch for Pale Moon Used to developed Unified XUL Platform - Fork of Mozilla code base which removes Servo and Rust