There is not much to say about VHDL support in GOSSIP right now. One possibility is to translate from a subset of VHDL to the native input language of gossip-sim. The subset will be chosen to support the simulation model of gossip-sim, synchronous data flow. Behavioural code will be translated into C++, using a modified version of the FreeHDL code generator, and structural code will be translated into hierarchical blocks written in Scheme.
Another possibility would be to interface gossip-sim with the FreeHDL simulator. This might be easier and provide more features. However, you would not have a fast synchronous simulator for a synchronous subset of VHDL.