We have two implementations for multiple context-free grammars. The first implementation is described here http://adp-multi.ruhoh.com/ and extends Robert Giegerichs Algebraic dynamic programming.
The implementation below on the other hand extends ADPfusion / generalized ADP. This allows us to implement MCFG grammars using our embedded domain-specific language for formal grammars. The algorithms implemented in this way show very good running time characteristics.