Hound vs Review Board: What are the differences?
Hound: A hosted service that comments on Ruby style guide violations in your GitHub pull requests. Take care of pesky code reviews with a trusty Hound. Hound reviews GitHub pull requests for style guide violations; 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.
Hound and Review Board can be categorized as "Code Review" tools.
Hound and Review Board are both open source tools. It seems that Hound with 1.72K GitHub stars and 393 forks on GitHub has more adoption than Review Board with 1.2K GitHub stars and 359 GitHub forks.