OpenProj is a project scheduling/management tool similar to GanttProject. It is also open-source and is written in Java. There is a gantt chart, there is a network chart, there are a few resource-related charts. It is developed by Projity, which is probably better known by their online service Project-on-Demand.
My personal feeling after playing with OpenProj a little is that the application is quite raw and unstable so far. There are obvious annoying bugs and quite a lot of usability problems. Goog luck for them, though! If they manage to overcome the problems, the community will be given one more nice project management application.