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Their claim is bending the truth. I've been using a Freeview USB dongle for well over a year and they've been around for longer.
Elgato hold the monopoly for Mac TV Tuners which is no bad thing as their software is very good and they offer a wide range of hardware. Elgato's software is also bundled with other manufacturers hardware.
I have the Miglia Mini with EyeTV 2.3 software.
I'd recommend looking at the choice on this page (link). If I were buying again today I'd got for the EyeTV Hybrid however for the iMac 400 you must look at the Eye250 (which supports USB1.1) or one of the more expensive Firewire models.