That's a slippery slope to saying that OpenOffice for Windows isn't free software either because you have to buy a Windows box. This is not a useful definition of free you're using. GarageBand is not Libre software.
I dunno if it's a slippery slope starting at Garageband. I say the slippery slope starts at OpenOffice or GoogleDocs or something along those lines, given that OpenOffice could probably be run on a potato if you can find a way to install ubuntu on it and stick some RAM into it.
