The DBTune MusicBrainz pre-NGS DB schema D2RQ mapping is a D2RQ mapping of a MusicBrainz pre-NGS relation database schema to knowledge representations that are powered by several Semantic Web ontologies, especially the Music Ontology. A newer effort of a mapping that is based on the MusicBrainz NGS schema can be found here (see also here and here).
The old project repository location at SourceForge is now deprecated. All new developments will be pushed to this repository location here at GitHub.