This doesn't have to be about "is DJing performance," but could be contingent upon a larger question about what is in scope for this site. I agree that the term "Music Software" is far too broad and should be clarified regardless of this larger outcome, but I don't think this definition should rely on Wikipedia in the slightest; after all, Wikipedia's music software category includes everything from the iPod's firmware to artificial intelligence.
I believe, rather, that our criteria for software questions needs to focus on the content of the question itself rather than the name of the program. Traktor is absolutely music software, but appears to be just as much iTunes as it is Ableton or Logic. If we decide that DJing is within scope, them library management in Tractor would be on-topic, as would some high-level questions about iTunes. Conversely, there are many artists that program with Max/MSP--a program that can be used for musical audio synthesis and processing, but can also control lights and visuals or anything else if you know a little Python.
I believe further discussion is warranted to come up with a 1-2 sentence criteria for question content related to software--not the easiest task, to be sure, but worthwhile to update the FAQ if we succeed and reach a consensus. The broader DJ scope question is being addressed in another thread.