Boscoyo is definitely busy getting more models in there. I'm actually surprised by how many they were able to get in there in such a short amount of time. When testing last week, there were only about 10 in there, so to see a majority of their catalog in there is awesome.
Other vendors are more than welcome, but they would need to talk to Sean. We do "charge" a yearly fee/donation for the marketing and it's really up to the vendor to decide if that's worth it to them or not. They would obviously also need to do the work to create the XML files and such to describe their products, create the models, etc.... It's not something a vendor will be able to do overnight or for free so they would need to consider their users and products and do what they think is best.