I want to make this, I need to learn actionscript - right?

Hey guys as a teacher who is done with his masters I have a summer ahead with a lot of free time and finally thought I would give some programming a go. I really want to make a site like this:

Dabbleboard - Online whiteboard for drawing & team collaboration - Interactive whiteboard software

for my students to use.

This site is obviously flash, so I am assuming learning actionscript and flash well help me reach this goal. Is that correct?

Is there a better language to attempt to achieve this in. It seems due to the visual interactive nature it would have to be flash.

And finally, i own Flash CS4, but not flash builder. Can I begin learning to code actionscript in Flash CS4 well enough that i don’t need Flash Builder?

Thanks guys.