This is just a bugfix release. I've modified the samples included in the mod file in order to avoid transposing notes when converting it with mod2gbt. This means that you can use all notes from C3 to B8.
You can find source, binaries and examples (RGBDS and GBDK) for version 1.2 here:
And any other improvements, here:
This is an old version, please, check this link for the latest release: