open-source pre-production software

A student mentioned celtx to me yesterday (thanks Matt). celtx is free pre-production software available to download from here. It works in a similar way to EP Scheduling but also has script formatting templates available and a simple storyboard pres-vis tool (so elements of FrameForge also. Best if all its free to use so looks fantastic value. Whether it will do same as FrameForge, EP Scheduling and Final Draft I don’t yet know but for no cost it seems to me to be really good value. Those three combined would be about £600.00.Had an initial look and am downloading it as I type so will post on it when I’ve had a chance to test it. Interested in its import and export abilities and integration with other packages as well as its overall features