The best open source alternative to Smartsheet is Redmine, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Smartsheet and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Smartsheet are OpenProject (Freemium, Open Source), GanttProject (Free, Open Source), ProjectLibre (Free, Open Source) and LibrePlan (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.
GanttProject is a cross-platform desktop tool for project scheduling and management. It runs on Windows, Linux and MacOSX, it is free and its code is opensource. What can it do? * Gantt chart. - Create work breakdown structure, draw dependencies, define milestones.
Baserow is an open source online database. Create your own database without technical experience. Our user friendly no-code platform gives you the powers of a developer without leaving your browser. Hosted and self hosted version available.
ZenTao is an open source project management tool, supporting Scrum. It integrates product management, project management, bug management and QA management, etc., covering all lifecycle of software development.