What are some alternatives?
When comparing Flyspray and Jira, you can also consider the following products
Mantis Bug Tracker - Mantis Bug Tracker is a free and open source, web-based bug tracking system.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Redmine - Flexible project management web application
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Trac - Trac is a project management and bug/issue tracking system. Provides an interface to Subversion and an integrated wiki.
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.