The best open source alternative to ClickUp is Wekan, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to ClickUp and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to ClickUp are Taiga.io (Freemium, Open Source), OpenProject (Freemium, Open Source), Kanboard (Free, Open Source) and Restyaboard (Freemium, Open Source).
OpenProject is an open-source project management software with a wide set of features and plugins. It supports project timelines / Gantt charts, issue tracking, wiki, document management, time and cost reporting, code management, Scrum and much more.
Kanboard is a simple visual task board software. Kanboard is a free and open source Kanban project management software. There is no fancy user interface, Kanboard focus on simplicity and minimalism. The number of features is voluntary limited.
Trac is an enhanced wiki and issue tracking system for software development projects. Trac uses a minimalistic approach to web-based software project management. Our mission is to help developers write great software while staying out of the way.
A Kanban-inspired app for keeping track of things that need to get done. The goal of TaskBoard is to provide a simple and clean interface to a functional and minimal application for keeping track of tasks. It's not trying to be the next Trello or LeanKit.
Foam is a personal knowledge management and sharing system inspired by Roam Research, built on Visual Studio Code and GitHub. You can use Foam for organising your research, keeping re-discoverable notes, writing long-form content and, optionally, publishing it to the web.