BUS1 continues advancing albeit it's not yet in the mainline Linux kernel and it isn't clear yet when it will be ready for merging. BUS1 continues seeing frequent commits to this out-of-tree kernel module.
A Phoronix reader pointed out that BUS1 now has a new sub-project: dbus-broker. BUS1's dbus-broker is self-described as a "modern D-Bus message broker", basically for brokering the exchange of D-Bus messages between two processes on the system. Dbus-broker is still in the very early stages of development and presumably will be a focus for offering D-Bus compatibility over BUS1.
There's only been a few commits so far but those wishing to monitor the progress of BUS1 can do so via this GitHub repository.