Thanks for an excellent intermediate tool that has Gantt and resource capabilities, but is not unduly burdened with features and options. It has just the right amount of "heaviness" for a project management system that allows collaboration within relatively small groups for consulting or software development.
A key feature that caused me to choose GanttProject was the very excellent and flexible CSV export. We use it for roundtripping to Google Calendar and then to local calendars in Thunderbird's Lightning add-on.
What would be cool is a slightly more capable import mechanism also using CSV. Properly labeled column heads corresponding to standard GP fields could then be formatted for better integration (for example, notes and dates as well as the basic task labels that is now the limit of the text import).
This may also be an easier intermediate implementation step to interoperate with Google Calendar that some have requested:
Thanks for your consideration and a very well-thought out tool.