Bug#858281: hydrogen: Please remove GMkit content from the package due to license

[Roberto]

Package: hydrogen
Severity: normal

Content under directory data/drumkits/GMkit is derived from non-free
sources (seems to be taken from Roland XV-5080 internal sound libraries).
The file data/drumkits/GMkit/drumkit.xml only says "undefined license".

Manufacturers of hardware synthesizers sometimes don't say which license
applies to their bundled sample libraries, but they are certainly not in
the public domain. They typically allow commercial content created with
them, without paying royalties, but they could complain if someone creates
a competing product derived from their sounds. A software synthesizer can
be seen as a competing product (there are precedents of this by Roland
Corporation in particular).

Moreover, please consider documenting all files under "data" directory in
debian/copyright, it will make easier to spot this issues, I've been using
the Roland samples in this package for years without knowing.