I am assuming you mean for time during the day. Parking at the resorts for a day trip does not cost anything for anyone,
DVC or otherwise, But parking is subject to whatever rules apply at the resort for such parking. And the rules that exist are designed to prevent people from parking at a resort just to go to a park. At BLT and other MK resorts, that usually means you can park there for up three hours if you have some confirmed event to attend at the resort like a restaurant reservation, but otherwise you will be turned away.
The exception I am aware of to that is valet parking. You can go to any resort during the day and valet park even if just doing so to go to a park. However, you may need to convince the parking attendant at the gate that you are actually going to valet park, and you can easily do that by also showing you are already valet parking at the resort at which you are staying (but valet parking does not exist at OKW or SSR).