Top 6 FREE and Open Source Project Management Systems in 2021

1- ProjeQtOr

ProjeQtOr is a free open source project management software grouping in a single tool all the features needed to organize your projects. It is simple, easy to use while covering a maximum of project management features. ProjeQtOr is designed as a collaborative tool, available in Web mode, and so requires the setup of a Web server. However, the installation is easy and automated as much as possible. To setup and run ProjeQtOr, a simple PHP / MySql stack is needed, you can use your favorite stack (EasyPHP, ZEND, WAMP, XAMPP).

Highlights
Multilingual (14 languages)
Cross-Platform.
100% collaborative (web based).
Web 2.0 user interface.

2- ZenTao

ZenTao is an open source project management software whose main features are product management, project management, QA management, document management, bug management and todo management. It is a professional Application Lifecycel Mangement(ALM) , covering the core process of software development. It also has powerful search features, various forms of statistical reports and complete API. ZenTao also has a Professional and Enterprise versions with additional features.

Highlights
Application Lifecycle Management.
Product Management.
Story Management.
Project/Sprint management.
Task Management.
QA management.
Bug management.
Case Management.
Planning management.
Release Management.
Statistical View.
Reports.
Kanban.
Whatsapp/Skype Group chat.
Open source and unlimited to commercial use.
Robust extensions and various plug-ins.

3- Tuleap

Tuleap is a free and Open Source Suite to improve management of software projects and connect with team members. It provides tools for managing projects, tasks, changes, defects, documents as well as version control, continuous integration and social collaboration. It has also a Professional and Cloud versions with more features.

Highlights
100% Open Source.
Monthly updates.
Project management.
Issue Tracking.
Git, SVN and Jenkins support.
Gamified Test Management.
Document Management.
Real-time collaboration.
4- Taiga

Taiga is a free open source project management platform for agile developers. It is simple and customizable. It has premium and enterprise versions with added features. It is programmed with Python, Django and AngularJS.

Highlights
Simple and customizable.
Scrum.
Kanban.
Import from Trello, Jira, Asana and Github.
Taiga REST API.
Taiga mobile app.
Social management.
5- TaskJuggler

TaskJuggler is a Free and Open Source Software project management tool. It covers the complete spectrum of project management tasks from the first idea to the completion of the project. It assists you during project scoping, resource assignment, cost and revenue planning, risk and communication management. It provides an optimizing scheduler that computes your project time lines and resource assignments based on the project outline and the constraints that you have provided.

The built-in resource balancer and consistency checker offload you from having to worry about irrelevant details and ring the alarm if the project gets out of hand. The flexible as-many-details-as-necessary approach allows you to plan your project as you go, making it also ideal for new management strategies such as Extreme Programming and Agile Project Management.

TaskJuggler is written in Ruby Programming Language.

Highlights
Powerful Todo list managment.
Full integration with Vim text editor.
Automatic resource leveling and tasks conflict resolution.
Unlimited number of scenarios (baselines) of the same project for what-if analysis.
Multiple time zone support.
Support for profit/loss analysis.
Comprehensive and flexible reports.
Project tracking and status reporting with dashboard support.
Projects can be combined into larger projects.
Powerful project description language with macro support.
Scales well on multi-core or multi-CPU systems.
Support for project management teams and revision control systems.
Data export to Microsoft Project and Computer Associates Clarity.
CSV data export.
iCalendar export.
Server based time sheet system for status and actual work reporting.
Runs on all Linux, Unix, Windows, MacOS and several other operating systems.

6- web2Project

web2Project is a Free Open Source business-oriented Project Management System (PMS). It is based on an AMP-stack which means it is designed to run on Apache, MySQL, and PHP.

Highlights
Role-based permission system to give the Project Manager fine-grained control over sensitive data.
Project and Group-wide Gantt Charts.
A unified calendar with iCalendar support.
A modular infrastructure which allows the addition or removal of modules to customize the features according to your requirements.

Reference
https://medevel.com/top-12-free-and-open-source-project-management-systems/