In fact, a number of other smart cover knock-offs are available, too.
Bovino's patent was awarded in Dec. 2005; he filed for it in mid-2003. The summary of US patent 6,977,809 says that the design is for a ruggedized case, one that also includes a strap for carrying the device.
A look at the images from the patent (shown) would seem to point to the ribs on the Smart Cover as being the most obvious similarity. The patent says that the case has:
"... a plurality of resilient ribs positioned on said exterior surface of said case wherein said resilient ribs protects said computer from wear and tear during the transporting and use of the computer."
Interestingly, it was reported earlier this week that Apple had been awarded a design patent for the Smart Cover.