The reason I said what I did was because I just assumed that since he was/is using a Gateway computer, that he wasn't using special studio monitors or any kind of interface with a bi-wired configuration or any other fancy deal. His last answer summed up the obvious though.
No, it will not harm your Mac in any way. But one question, are you able to just remove the chord from the speakers and use just a single chord (one you'd buy at Radioshack) instead of that split one? If so, then it's fine.
It would be helpful if you could post a photo of these speakers, too.
Doug