Jerome A. Cohen of the US Asia Law society explains that Ai Weiwei’s release on qubao houshen doesn’t literally mean “bail”, despite its common translation. In this case, since no formal charge has been made against him — apparently he never even “formally arrested — it’s impossible to release him on bail. The announcement only claims Ai has confessed to crimes.
So what is Qubao houshen? As told by Cohen,
Qubao houshen (QBHS) is a technique that the public security authorities sometimes use as a face-saving device to end controversial cases that are unwise or unnecessary for them to prosecute. Often in such cases a compromise has been reached in negotiation with the suspect, as apparently it has been here. Of course, we will have to hear what Ai says upon release, recognizing that, as part of the agreement and as a consequence of long incommunicado detention, the released suspect is usually subdued in any public remarks made upon release (recall Xu Zhiyong, for example).
…The decision to grant QBHS has little to do with the rule of law, but everything to do with the untrammeled exercise of discretion enjoyed by Chinese authorities. This outcome makes clear that great international public pressure plus significant domestic and personal guanxi (å…³ç³», connections) can be a potent combination even in the case of someone who went further than anyone before him in openly thumbing his nose (and other body parts) at the Communist regime. Undoubtedly, Ai's star talent, his family history and global support from the artistic community helped a lot.