No, you cannot let people download an OBJ file made from the P4 characters. You will either have to distribute just the CR2, not the OBJ, or you will have to use a program like RTEncoder, so only people who already have the OBJ can use your file. If you post an image of what you've done, people could probably give you more advice on how to legally distribute it.

Rendered images made in Poser are yours to do with as you will. Give them away, sell them, put 'em on t-shirts - as long as it's your own render, it's yours.