Flash isn't an open standard by any useful definition.
Sure they specified the container format and data structures (just like with the MS Office formats), but everybody had figured that part out a long time ago because it's obvious and easy to capitalize on by developing an extractor. The runtime APIs are incredibly hard to reverse-engineer, comprise the vast bulk of the Flash implementation, and are the entire reason for the plugin's instability.
Sure they specified the container format and data structures (just like with the MS Office formats), but everybody had figured that part out a long time ago because it's obvious and easy to capitalize on by developing an extractor. The runtime APIs are incredibly hard to reverse-engineer, comprise the vast bulk of the Flash implementation, and are the entire reason for the plugin's instability.