hplip included questionable licensed code.
This license is "hardware specific" license.
It is non-free, incompatible GPL license.
This is code (software), not firmware.
This problem already reported. (Debian)
I suggest that resolve license problem.
Created attachment 1188843 [details]
I removed files with proprietary license and disabled features using it (PCL3GUI2). Package was built in RAWHIDE.