The Waterfox source code is a specialised modification of the Mozilla
platform, designed for privacy and user choice in mind. You should be
able to install it and compile Waterfox without any issues. Other
modifications and patches that are more upstream have been implemented
as well to fix any compatibility/security issues that Mozilla may lag
behind in implementing (usually due to not being high priority). High
request features removed by Mozilla but wanted by users are retained
(if they aren't removed due to security).

Features:

 o Disabled Encrypted Media Extensions (EME)
 o Disabled Web Runtime (deprecated as of 2015)
 o Removed Pocket
 o Removed Telemetry
 o Removed data collection
 o Removed startup profiling
 o Allow running of all 64-Bit NPAPI plugins
 o Allow running of unsigned extensions
 o Removal of Sponsored Tiles on New Tab Page
 o Addition of Duplicate Tab option (toggle with browser.tabs.duplicateTab)
 o Locale selector in about:preferences > General

WWW: https://www.waterfoxproject.org/