As far as the legal considerations go, Rob has OK'ed this relationship. As far as permission from musixmatch goes, they have given it in person (myself and others at the summit are witness to this).
There has been no discussion on the style list, presumably under the impression that the above would be enough. However, it has not been covered whether or not people actually consider musixmatch a useful resource to link to, or whether the "license" is acceptable (I don't know what this means) - I hold no opinions there because I don't dabble in style 
Shall I revert my changes until this has happened?
Updated ticket description with actual implementation.