doubleTwist is a widely-used, legitimate piece of software. I'm not sure why it would set off Symantec, but it's hardly a skeezy fly-by-night. This is the new company that Jon Johansen (a.k.a., 'DVD Jon,' the guy who cracked DVD CSS encryption) started up. They've been written up quite often, profiled as a company by Wired and various newspapers, etc.
Their overall aim is apparently to create an iTunes-like interface for everything that isn't an iPod; they sync to Android, Palm Pre, a number of random music-phones, various media-players, and even present the Amazon MP3 store in an iTunes Store style interface, integrated into the client.
Now, I don't actually care for doubleTwist that much; I think the software still needs a lot of work. But they're still hands-down the easiest way to do fairly trouble-free synching onto a Palm or Android device, and they're definitely legitimate. And they're available on both Windows and Mac OS X.
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