As the USB port is just an add-on option with an HP 4050, you could as well connect the 4050 to your beige G3 via ethernet (Ethertalk). You will just need a proper cable (10BaseT, maybe a cross-over type of cable). The G3 has ethernet already in the 10BaseT version.
Alternatively to the HP driver software, you may try Apple's LaserWriter driver software as well that came with your OS, called "LaserWriter 8" in Mac OS 8 packages for example.
Good luck,
Walter.