No, you don't have to pay. I have heard that sometimes they make you show them a ressie if you have one for a restaurant you're going to at a different resort. I've driven to different resorts while I'm down there and I've never had a problem with them letting me in. I've always said that I wanted to drive around the resort and see what it's like and they usually have no problem. I've even gotten maps and tips on where to go
Now, from what I've heard, if you do have a ressie...say at Boma at AKL..and you're not staying there, I've heard that you have three hours to be there. I don't know how true this is, but it's what I've heard.
NOW..this other part I'm getting ready to say is not by ANY MEANS me telling you something that's a "rule breaker" or that's gonna get you into trouble, but this is some other things I've heard:
~If you're going to be a park the day you have a ressie at another resort, I've heard that you can just catch that bus/boat back to the resort and there's no problem.
~If you don't want to drive, then hop on the bus that takes you to DTD(downtown Disney)and switch buses and go back to the resort that you're having your ressie at.
These are the two main things I have heard....and I've heard about them from on here...the DIS. SO I don't know the exact protocol for it, but I don't think you have to pay to park there. The only parking that I know you have to pay is at the theme parks, if you're not a resort guest.