Well Neal… maybe it’s time to install the software on an OS X bootable partition, or on a separate OS X based drive within your G4 AGP… at least for scanning tasks?
Lacking an actual HP 1510PSC here, I attempted a comparable / similar install of an Epson Workforce 610 (scanner, printer, fax) of similar mfg. era here last night. And while the Epson also touts possible use under OS 9.2… I couldn’t get it to respond at all under OS 9.2. Zip, zero, nada.
However (on a dual-boot Quicksilver / OS 10.4) with the same Epson software installed, printing and scanning works very well. And, I have read that this Epson 610 will print (under OS 9.2.2) but won’t scan. If I needed to print from 9, then I might consider scrounging around for a suitable printer driver OR simply transfer text docs, image files or word processing etc. from OS 9 to X.
And, might be comparing apples to oranges between the HP and the Epson… but in order to have the Epson 610 function, not really that much of a hassle to scan, print. etc. under OS X and then one could always transfer or write the image scan files to the OS 9 drive (or partition) should one need them in OS 9 for any reason.
Sorry this doesn’t “fix” your OS 9 quest …but it might be a stop-gap workaround for your needs?
What you seek may indeed be “out there”… I just can’t find it. Maybe someone else can?
A similar quest / thread:
http://macos9lives.com/smforum/index.php/topic,3861.msg26000.html#msg26000