Credits

QMP3Gain written by Zsolt Branyiczky

MP3Gain back end by Glen Sawyer

ReplayGain idea, concepts & website by David Robinson

Control buttons by Marc Heubeck

Help file by Zsolt Branyiczky based on Bill MacEachern's work

The latest version of QMP3Gain can be found at http://qmp3gain.sourceforge.net/

The latest version of MP3Gain back end can be found at http://mp3gain.sourceforge.net/

For more information about ReplayGain analysis, please see the ReplayGain website at http://replaygain.hydrogenaudio.org/

QMP3Gain is completely freeware. No registration, no time limits, no disabled features, no annoying pop-up messages, or anything like that. There will always only be one current version of QMP3Gain, and that version will always be freely available to everyone.
With that said, if you really like this program and feel like making a donation to the author, you can find the appropriate information by clicking Help > About in the menu of the program itself.