How are HPLIP and HPIJS related?
HPIJS is a subcomponent of HPLIP. HPIJS provides basic printing support for non-postscript printers. HPIJS can operate in any spooler environment (including no spooler). HPIJS provides no I/O. HPLIP provides I/O for bi-directional communication, scanning, photo card access, and toolbox functionality. HPLIP requires the CUPS spooler.