Redmine can be run on top of Apache and Nginx using Phusion Passenger or in any other environment where one can deploy a Rails application. It supports multiple users, multiple projects and access control settings. Authentication can be done using LDAP or using OpenID.
Redmine includes support for issue tracking features, documentation using wiki functionality, time and project management (including Gantt chart production), and integrates with version control repositories including Subversion, CVS, Git, Mercurial, Darcs and Bazaar. It is possible to install themes and custom extension modules.