This is a VGM player I've written for the original monochrome Gameboy (and Color/Light/SGB/Advance).
You can download it and the source code here
And you can see/hear it in action here
It obviously doesn't cover all the chips supported by the VGM format. Only the SN76489 is emulated (used in Sega Master System and Game Gear).
Since the waveform channel on the Gameboy only has 4 different volume settings it'll probably sound weird in some songs. Loading new waveforms dynamically to simulate 16 volume settings didn't seem like a good option.