Feel like I'm pretty close to getting this to work with Call of Duty: World at War. Game shows up in XMB, I click on it, game goes back to XMB, no error. Previously was getting the typical 80010006 or w/e it is error until I switched it to a hard drive game in PARAM.SFO. Firmware version 4.78.
Interestingly, though, even when I was getting the error, the game still attempted to launch. Trying it with MW3 just errors as soon as I click on it.
According to the Russian forum, it's related to LIC.DAT/EDAT, and older games (such as WaW, Afro Samurai, etc.) do not have a LIC.DAT/EDAT check.
I'd be willing to bet that the Backup Utility blocks EDATs from the unprotected archive (at least on firmwares higher than 4.70), hence why no game with an .EDAT check actually boots, because there isn't one on the hard drive. However, the Data Transfer Utility DOES copy those LIC.EDAT files, and that is why the newer games work.
Will keep trying and let you all know. No way I'm updating to 4.8/4.81, though! (PSN bypass still works on 4.78, so I've been using it for a long time now).
Update:
Tried Unreal Tournament III, which is another old game out of my collection that doesn't have a LIC.DAT check. I am able to boot the game, but it stays at an eternal black screen. It's likely I didn't copy all the necessary files or something. The system doesn't crash, though, because I can open the XMB. However, it does reboot the PS3 if I try to exit the game.
There is something to this method after all. I know these games will work, I just haven't figured out exactly how to make that happen. I'm close, though. Once I figure out a foolproof way of doing it, I will post a full English tutorial with pictures.