ActionScript 2.0 does not have any system requirements in addition to Flash.

Flash CS3 Professional introduces ActionScript 3.0. Flash Player 9 and ActionScript 3.0 are the default publishing settings for Flash. This manual provides information on how to use ActionScript 2.0 with Flash. You must change the publishing settings for your Flash files to Flash Player 9 and ActionScript 2.0. If you do not change the default settings, explanations and code samples in the documentation might not work correctly. If you develop applications for earlier versions of Flash Player, see Writing Scripts for Earlier Versions of Flash Player.