Phabricator vs Review Board: What are the differences?
Phabricator: Open Source, Software Development Platform. Phabricator is a collection of open source web applications that help software companies build better software; Review Board: Stress-free code review for teams of all sizes. Review Board is an open source, web-based code and document review tool built to help companies, open source projects, and other organizations keep their quality high and their bug count low.
Phabricator and Review Board can be primarily classified as "Code Review" tools.
Review Board is an open source tool with 1.2K GitHub stars and 359 GitHub forks. Here's a link to Review Board's open source repository on GitHub.