Aacgain 1.9 had been ported to OS/2 and eComStation (2017/03/04).
"Aacgain is a modification to Glen Sawyer's excellent mp3gain program. It supports AAC (mp4/m4a/QuickTime) audio files in addtion to mp3 files."
Official Project URL: http://aacgain.altosdesign.com/
Port by Gianfilippo Cimmino
Source: eCSoft/2