GanttProject is a cross-platform desktop tool for project scheduling and management. It runs on Windows, Linux and MacOSX. (GPL)
Cross-platform
Jobsworth can be used for helpdesk support ticketing, customer liasion, resource management (eg. systems and password tracking) and has a range of CRM type functionality. Plan your projects, see your schedule, know if you're slipping behind and why (AGPL)
Cross-platform
With Jorani you can deploy a workflow for the leave and overtime requests of your organization. When creating en employe, specify its line manager and this manager will receive by e-mail the leave and overtime requests of its collaborators. (GPL)
Cross-platform
LibrePlan is a collaborative tool to plan, monitor and control projects and has a rich web interface which provides a desktop alike user experience. All the team members can take part in the planning and this makes possible to have a real-time planning. (AGPL)
Linux
OpenProject is a web-based project management system for location-independent team collaboration. Open source project management software. Powerful. Easy-to-use. Free. (GPL)
Cross-platform
Orchard Collaboration is a free, open source ticketing system, project management and collaboration framework. It integrates with Orchard CMS and extends its features by allowing its users to collaboratively work on the content. (GPL)
Windows
Plan is a project management application. It is intended for managing moderately large projects with multiple resources. (LGPL)
Linux - FreeBSD
Project-open is a web-based "Enterprise Project Management" software for project-based organizations with 2-200 users. Project-open integrates areas such as CRM, sales, project planning and tracking, collaboration, invoicing and payments. (GPL)
Cross-platform
ProjectLibre desktop is a free and open-source project management software system intended ultimately as a standalone replacement for Microsoft Project. ProjectLibre has been downloaded 5,500,000 times in 200 countries on all 7 continents and translated into 29 languages. (CPAL)
Cross-platform
qdPM is a free web-based project management tool suitable for a small team working on multiple projects. You can easy manage Projects, Tasks and People. Customers interact using a Ticket System that is integrated into Task management. (GPL)
Cross-platform
Redmine is a flexible project management web application. Written using Ruby on Rails framework, it is cross-platform and cross-database. (GPL)
Cross-platform
SoFreakingBoring is a free and simple project management and time tracking application. It allows you to easily create your own projects and tasks, invite people and start working together. (MIT)
Cross-platform
Todoyu is a new, modern and award-winning open source project- and task-management system. Working with todoyu is simple, efficient, time-saving new, modern and straightfoward. (GPL)
Cross-platform
13 applications