What are some alternatives?
When comparing Calligra Plan and GNOME Planner, you can also consider the following products
GanttProject - Project scheduling and management tool
Microsoft Project - Microsoft Office Project gives you robust project management tools with the right blend of...
Taskjuggler - TaskJuggler is a modern and powerful, Free and Open Source Software project management tool.
FoxPlan - Web-based project collaboration tool
LibrePlan - LibrePlan is an open source web application for project planning, monitoring and control.
Basecamp - A simple and elegant project management system.