Many of the tuners have the unlimited license for HP Tuners for the Gen III PCM's, I'd have to go look at HP Tuners website to see how many credits you need for a particular type before you end up unlimited, but it's likely a 'tuner' would not need to purchase any credits.
Ok I looked briefly, here's a thread on it -
https://forum.hptuners.com/showthrea...ed-gm-gen-3-v8
There are new tools out there besides HP tuners that allow you to tune for free also. For example...
I had my harness touch my exhaust and it grounded out one of the injector trigger wires from the PCM, caused the injector to stay open all the time. Was lucky to not hydrolock the engine with fuel. I was getting white 'smoke'(fuel) out one tail pipe. Tail pipe smelled like gas.
I fixed the harness and the engine ran fine, but I had a code that I could not get rid of. Something related to injector trigger can't remember the number.
I troubleshooted it down the the only possible problem being the PCM. If I swapped the PCM, that would mean I would have to buy more credits from HP Tuners for the new PCM.
I ended up buying a OBDLink LX and used PCM Hammer to clone my old PCM to the replacement. Worked great and that code has not returned.
That really opened my eyes, if I had another swap vehicle with a Gen III engine, I could just make another clone of my PCM and wouldn't need more credits.