Seen the requirements, I hope you don't mind if I suggest XPlan. Not open source, but no subscription fees too. Customizable and with hierarchies.
Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink.
Hide child comments as well
Confirm
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
Seen the requirements, I hope you don't mind if I suggest XPlan. Not open source, but no subscription fees too. Customizable and with hierarchies.