Redmine

Redmine is a mature, flexible open-source project management and bug tracking tool written in Ruby on Rails. It is a champion of self-hosted, cost-effective solutions, allowing organizations full control over their data and infrastructure. Redmine supports multiple projects, wikis, forums, time tracking, and Gantt charts. Its functionality can be extensively extended through a vast library of community-developed plugins, enabling features like Agile boards, improved UX, and advanced reporting.

While its default interface is functional rather than beautiful, it is highly capable. Redmine is ideal for tech-savvy teams, educational institutions, and organizations with strict data privacy or budget constraints who have the internal resources to install, maintain, and customize the software. It serves as a powerful, no-license-fee alternative to commercial tools, though this comes with the trade-off of requiring your own administration and lacking official support unless purchased.