I'm not too sure about this,but .swf is used for flash widgets from what I can tell,and that's about it.I don't know what you mean by that,but you would need to create your game in a flash program in order to submit it here on AG.
well um yes of course flash costs money,and its not something simple where you take a bunch of pre-made stuff and put it together.Real video game design is not something to be taken lightly.Th reason why flash costs money,is b/c if you get your games sponsered then you can make a profit from them.
SWF = ShockWave Flash. It is owned and developed by Adobe Systems. It is an open format as of May, though it is not widely supported outside of Adobe's Flash. You can not upload anything other than .swf format files as they do not offer in-browser viewing.
I forgot Dank knows alot about programs so he probably would have known that better then anyone else on here,except possibly ubertuna,but still he did create his own website and I think he creates flash games that he puts on it.Point is now that the question has been officially answered fully,it would now be appropriate to lock this thread.