Honestly, that's how I'd rule it. But, playing exactly as it's written, the "harms other creatures" bit is little more than flavor text. It clearly demonstrates the intent of the spell, but provides no limitations for using it as such.
I see no reason why the spell would have to come from the...
That's reasonable, but what about spells that are ambiguously harmful? Polymorph meets the qualifications for GoW (at higher levels), but could be positive or negative (obviously it would only be positive against certain monsters... or people that really, really like dolphins).
I think what's...