An offset of 15 means that the distance from the center point of the wheel to the mounting surface that mates to the hub of the Jeep is 15mm. Since it is a positive 15 on this wheel, that means that the mating surface is closer to the face of the wheel than to the rear of the wheel. On a 9" wheel, this equates to a backspace of 5.6". I wouldn't recommend that large of a backspace with a 285 tire personally. You could might be able to get away with it, but I would try to find a wheel that was closer to that magic number of 4.5" backspace. The larger the backspace, the closer the wheel and tire remains to the suspension components, airdam, etc. This increases the likelihood of rubbing and contact.
Here is a handy dandy app you can play around with.
Custom rims, wheel tire packages for your ride - RIMSnTIRES.com
For visual reference, here are my 285s mounted on wheels with 4.5" backspace. The wheels you are looking at would be tucked under the fender a full inch further than this.