You'll need some kind of IO port. I would guess that the 8085 microprocessor kit has one built in that you can use.
The irony of it all is that the keyboard probably has a more powerful microcontroller than the equivalent 8085 microprocessor kit.
Yes, I agree with that position. The problem was to interface, and I didn't see anything that said I could not use a host controller chip to do the job. You'd still have to come up with the USB host stack in 8085 assembler or maybe PLM(ughhh...) Still a challenge but not impossible. If it was a Z-80 I could probably dig up Leor Zolmans BDS-C compiler and have some chance of porting an existing USB Stack.