Q:

Adobe Flash Developer License Cost

I want to develop a flash application, I would like to know how do I go about buying a license to develop using flash and also if anyone has an idea as to what the cost is.

A:

You can create content for the FlashPlayer with a number of free (as in freedom) tools.
You can either use ActionScript 3 and MXML and compile it with the Flex SDK. For Windows I suggest FlashDevelop as an IDE. It will download the Flex SDK for you and you can start to code right away.
Another alternative is Haxe. The Haxe compiler can target the FlashPlayer (and many other platforms). The aforementioned FlashDevelop also has excellent Haxe support.
There's also a line of commercial products from Adobe for flash development, which includes the designer-centric Adobe Flash Professional and Adobe Flash Catalyst, as well as the developer-centric Adobe Flash Builder. And there is quite a number of 3rd party tools, FDT being the most noteworthy for developers. Also a free version has become available recently.
Personally, I don't recommend any of the commercial tools I mentioned, but each of them has a 30 day evaluation period (or more), in which you can see for yourself. Typically these products have prices starting at 500 USD for commercial licences.

