Is there a open source alternative to flash. I love to create flash games but flash is very expensive :(.
If you are talking about the IDE, I would recomend FlashDevelop using Flex SDK to compile. You will have to code everything with ActionScript, so no Timelines or any of the FLash IDE goodness (or badness if you like :) ). Here is a tutorial on how to get started:
http://abrahamyan.com/2008/11/28/how-to-setup-flashdevelop/
Also have a look at Haxe, it integrates seamlessly with FlashDevelop and you can generate swf files with it.