Under Apple’s EULA, installation of Leopard onto any computer equipment other than Apple’s own hardware is prohibited. If the past is any precedent, the company should be shortly contacting Psystar with a cease and desist request.

However, Psystar appears ready to fight, suggesting the clause forbidding such installations are a violation of US antitrust laws. Until then, it will continue to sell the OpenMac clone for $399.The $399 OpenMac’s base configuration includes a 2.2 GHz Intel Core 2 Duo processor, 2 GB of DDR2 RAM, Integrated Intel GMA 950 Graphics, a 20x DVD rewritable drive, and 4 rear USB ports.

A higher-end version, the OpenPro, retails for $999. The base configuration there includes a 2.6 GHz Core 2 Duo, GeForce 8600GT graphics card, 600 watts of power, 3 120mm fans, standard FireWire ports and front USB ports.

For both systems, Leopard is available preinstalled for an additional $155. On the Pro, additional systems other than Apple’s can be installed.

“You don’t need to spend an arm and a leg to get the full OS X Leopard experience,” Psystar says on its Web site.

Psystar officials are comparing Cupertino’s restrictions to Microsoft saying Windows could only be installed on Dells, or a car company telling you which roads you could drive on.

Either way, this offer does not look to be targeted to the average consumer. A quick perusal through the company’s FAQ indicates that a user may not be able to always use the upgrades from Apple because some may be “non-safe,” and the Web site seems to target the PC to the “experienced” user.

Apple could not be immediately reached for comment.