Sure you can edit the project file however you like with the build program within the rules/laws of the end user agreement license (EULA). What you are not allowed to do is decompile or reverse engineer the resulting final output files.
I didn't make the rules, I'm just explaining them the best way I can.
Lets say you see a nice design in a Flash file that you didn't make and thought hmm, that looks great and decompiled the Flash file and "stole" the portion you though was worth taking and used it for your own work. It is still classed as stealing. If you decompile a file you created with software you have a license for and this gives you access to the developers code that you were never entitled to see you again are breaking the law and the EULA.
I understand you personally don't want to do this, you only want the modify the fullscreen menu bar but, reverse engineering is reverse engineering and that is against the policy of your license.
If you were allowed to have access to the Flash file and all it's make-up you would be offered the .fla version and not just the .swf version.
This is the case with the "Loader" and "Fullscreenbar" within the resource folder of Tourweaver. The problem is as I have already explained is that the fullscreenbar.fla doesn't contain the AS3 that controls the actions it is hidden elsewhere in another file. This make the access to the fullscreenbar.fla file useless apart from changing the HUE of the images that make up the file.
Bottom line, the .swf file is meant to be an un-editable final file. Adobe even state this. Just because decompiling software exists doesn't make it legal to use.