Yes, there is a difference between the standard SME printing system, LPRng, and CUPS. For instance, CUPS doesn't use printcap to specify input filters like LPRng does, which means that the printcap template fragments from the overlay package you refer to won't have the desired effect. Also, the PCL macro filter itself doesn't conform to CUPS filter specifications, so would need some modification. You'd also need to make a PPD that instructs CUPS to send PCL input through the PCL macro filter. If all that doesn't sound like your idea of fun, you might be better off getting LPRng to work properly. Updating the e-smith-LPRng package, as dicussed numerous times in these forums, might be all that's required. If you do wish to convert the PCL macro filter to a CUPS filter, a detailed post to one of the CUPS mailing lists might be worth a try.