Though the adoption has fallen, ActionScript 3 was a near strict improvement over 2, and it was released a good while after the Macromedia acquisition.
It was primarily developed at Macromedia, if you don't count that Waldemar Horwat and others greatly influenced its design via the whole JS2/ES4 situation in the years prior. That's why AVM2's IR used to be called the Macromedia Intermediate Representation, for example.
There were public betas available about 6 months after the acquisition, which didn't leave Adobe much time to change anything. Even the main APIs, like those in playerglobal.swc, almost all have a copyright stamp of 2005 in them.
