The GTRACT documentation on the slicer wiki 

http://www.slicer.org/slicerWiki/index.php/GTRACT_V4#Installing_GTRACT

says that binaries can be downloaded from NITRC, but I only

see version 3 binaries on NITRC.

http://www.nitrc.org/frs/?group_id=77

Can GTRACT v4 only be built from source?