Well, just incase here's the jist of the East of The Mississippi contract...
EAST OF THE MISSISSIPPI – ANY OTHER THEME PARK IS LIMITED TO USING CHARACTERS NOT CURRENTLY BEING USED BY MCA AT THE TIME SUCH OTHER LICENSE IS GRANTED. [FOR PURPOSE OF THIS SUBSECTION AND SUBSECTION IV, A CHARACTER IS “BEING USED BY MCA” IF (X) IT OR ANOTHER CHARACTER OF THE SAME “FAMILY” (E.G., ANY MEMBER OF THE FANTASTIC FOUR, THE AVENGERS OR VILLAINS ASSOCIATED WITH A HERO BEING USED) IS MORE THAN AN INCIDENTAL ELEMENT OF AN ATTRACTION, IS PRESENTED AS A COSTUMED CHARACTER, OR IS MORE THAN AN INCIDENTAL ELEMENT OF THE THEMING OF A RETAIL STORE OR FOOD FACILITY;
From that I believe means is that any character being shown within said park can't be used at WDW..Not sure how it complies with the Marvel super hero store At the springs as many of the characters are representend inside..