I\'ve never developed Flash before but I have a project where I want to use an ActionScript 3 library and I\'m not sure what tools I need to start. To further complicate thi
A Windows or Mac box. :-)
just kidding, actually you can use the Flex 3 SDK mentioned above and compile using the CLI. If these AS3 Libraries are indeed Flex libraries (sometimes there are discrepancies between what works in Flex, what works in CS3, and what works in both) then you should be able to import them and use them.
Also, I've never tried it myself, but Flex Builder is based on Eclipse and I believe there's a way to configure Eclipse to compile with the opensource Flex compile if you'd rather work in a graphical IDE.