No it does not and probably will never have. The .dbc file format is a proprietary format of the Vector Informatik GmbH and they want to make money with it. I don't want to be sued for reverse engineering the format. Kayak is open source so if you need support for .dbc develop a plugin on your own.
I think JNI is something that should be avoided if possible. Your code tends to get ugly and you can
easily run into various problems.
The new attempt in Kayak was choosen because it has some advantages and creates new possibilities how you can set up your infrastructure.
Yes this is possible. Currently there are no attempts in this direction but it should be quite simple to implement.
It is possible to run the socketcand and the SocketCAN backend in a virtual machine and connect to this machine with Kayak. The performance may not be the best but you can do this...
Yes sending is possible via the Send view
No this is not yet possible but it should be fairly simple to implement in a plugin.