Prosecution for that offense was declined. It says nothing about prosecution for any and all other offenses. It's really a small beans crime and while rule of law rules, prosecutors aren't gonna take up a case involving an FBI SA when they're bringing a metric fuck ton of charges against some heavy hitters for FAR worse. That'd be called managing caseload.
Shit, even if he did kill bin Laden, he should still keep his fucking mouth shut. The Teams hate these kinds of people. Fame whores. SEALs don't seek fame or recognition, just look at Chris Kyle as an example. He threw his weight around to help others, not himself. Something about O'Neill has never sat right with me. Probably because of the whole "look at me! Look at me! I killed me an Osama!" shit.