Digital Photography Review reports: [edited]
LightZone is powerful raw image file developer and editing software, with a polished, pleasant user interface and decent help files. Online forum support is available and it has a growing, active user community.
LightZone 4.0 is now Free (as in Freedom) software and it is available from Lightzone.org under a BSD license for Windows, Mac and Linux.
LightZone uses the dcraw library to open raw files, software that is well maintained and periodically updated.