Wait a minute, I'm feeling my inner Doryphore coming to the surface: TTBOMK, if Aldridge filed official retirement paperwork with the league, then he should be required to sit out for a minimum of two seasons. And, if he didn't file official paperwork, then shouldn't Brooklyn still own his rights, meaning that he was not a free agent?
At any rate, I hope that he was actually given a clean bill of health, and didn't just keep looking around until he found a doctor who was willing to clear him to play basketball.