You can publish using any version of Gamestudio. However, if you buy the standard edition, you will have to display an A6 watermark on the game at all times. If you upgrade to the extra edition, this no longer applies. However, in all editions except for Pro, you do have to display the A6 logo at the beginning of the game for 1 second.
As for an audio editor, there is none available with the Gamestudio package. However, there are a ton of free editors you can find on the internet. The first that comes to mind is Audacity, at
http://audacity.sourceforge.net/. This is a very good free editor. I use it all the time to record guitar, and while I do not have a very high quality mic, it still comes out good. Gamestudio does support various sound file formats. The standard edition only supports .wav and .mid, however. You will have to go all the way to commercial to do any better than that

.
Anyways, hope this helps,
Raddaddy