VGMSlap (VGM Silly Little Adlib Player) is an open-source, MS-DOS based player for Yamaha OPL1/2/3 Video Game Music (VGM) files. It features a visually pleasing display of each synthesizer channel's parameters, GD3 tags, and simple playlist support.
See the program readme (VGMSLAP.TXT) for additional info.
VGMSlap is written with Open Watcom C 2.0 in mind. Assuming you're on DOS/Windows and you have your Watcom environment variables and PATH set correctly, the following command should build VGMSLAP.EXE:
WCL -bt=dos -mm -wx -otexan -fe=vgmslap.exe vgmslap.c ./zlib/zlib.lib
You may need to modify this slightly if cross-compiling from Linux (probably just the path to zlib.lib).
The VGMSlap software and code itself is licensed under the MIT License (see LICENSE).
This VGMSlap source distribution also incorporates a prebuilt zlib 1.2.11, the last version I could get to successfully compile for DOS on Watcom, which is licensed under the zlib license (see zlib/LICENSE).