If the game is compiled as an 64-bit application, then it can use more than 4GB RAM and will most likely also perform better (faster loading times, less frame-drops, ability to add more effects without a performance impact, etc).

Nothing you can do about this apart from asking the developer to consider compiling a 64-bit version of the game as well.which may or may not require additional programming to the game. If the game is compiled as an 32-bit application, then the 4GB limit is going to stick regardless of the amount of physical RAM in the machine.

The memory limitation comes from the way the game is compiled with regards to architecture.