It seems like Yoochun will remain a free man without spending any time in prison.
Prosecutors have announced that they will not be pursuing an appeal of Yoochun's 2-year probation sentence for drug use, and it was further stated that his sentence was due to the fact that he had a previously clean criminal record.
Yoochun was recently sentenced to two years of probation and fined 1.4 million KRW (~1200 US dollars) and will have to serve a 10-month prison sentence if he violates his probation.
Public opinion of Yoochun is still cold, and many feel that he has received an incredibly light sentence. The fact that he also initially lied regarding his drug use and his initial unapologetic attitude is constantly cited and netizens are not looking upon him with sympathy.