Question about LPC Art license

Question about LPC Art license

Hello, I'm entering pre-production on a free 2D ORPG using an open-source C# engine and I was wondering if I'm alowed to use the LPC artwork for a prototype of my game which will be used to generate insterest to bring on new artists to replace the LPC artwork with custom artwork. Can I do this or will my project have to remain open-source until the artwork is replaced?