The last word Decisive Tactics has on Printopia Pro (as of this writing) is there were some fixes in June for issues in 10.7:
Printopia Pro Release Notes

Just in case anyone’s curious, I loaded Printopia Pro on a Mac running Sierra (10.12), and it’s running just fine. No official word from Decisive Tactics, but it works, in case you’re itching to upgrade (I can’t make guarantees—I can just attest to one scenario in which it works).