myx your own ringtones

So many of yall may have already heard of myxer.com but for those, maybe few, who haven't, I thought I'd share the love. It's a website where you literally can mix your own ringtones by choosing the portion of a song you want, what duration, and if you want it to repeat for FREE. Some you have to pay for, but there are people who individually put the songs on the site on their own that cost nothing to edit and make your own. I'm not entirely sure how the logistics of the site work and if anyone can answer that for me, that'd be great. Obviously they make their money through advertising on the site, but what I want to know is how is everything they're doing is legal? With the ringtones being free and all... we'll see. I tried to look it up, but didn't find any sort of substantial answer. But, anyways ENJOY MYXING.