The datasheet on the USB interface chip should be retrievable. If one additionally traces the PCB one could create a new FPGA binary for the existing hardware. The other method is to debug the existing driver and use that as a reference to get the API, and build a new driver from that.
Neither is rocket science, it's just hard and takes some time.
These things will happen over and again as long as people let them self depend on closed software or hardware.
The FPGA on the Deneb is pretty sophisticated. I don't think it would be easy to write a driver for it without docs. Then again, I wouldn't see a reason why E3B should not publish the necessary docs.
And speaking about reverse engineering to get the API: This is not necessary. The API is the same as in the AROS and MorphOS versions and I think the docs are in both the MorphOS SDK and AROS source tree. And you could still look at the open source code to find out the meaning and use of some device fields if they weren't already obvious. Ah yes, did I mention that the pciusb.device is also open source?
And about rocket science: A programmer was able to hack the deneb driver binary to some other SecretHardware(TM) within two days.