> Phabricator is nice, but it's more of a full-featured replacement for GitHub as a whole. Some people want to keep most of GitHub and just improve on the code review aspects.
That's the nice thing about Phabricator, you can switch off all features you don't need, and it integrates with GitHub. You can definitely use it just for code reviews, with users logging in using their GitHub accounts and the repositories being hosted by GitHub.
> You can also deploy Review Ninja (and soon Reviewable) on-premises, though of course that means you're on the hook for administrating the system again.
That would work! Third party SaaS probably includes Github.
This is one of the finest pieces of open source software that I've ever seen. The documentation is very good and even succeeds at making LaTeX accessible to non-technical people.
I've been using it for years for pretty much everything that other people would use LibreOffice or Office for.