It looks like your son is pretty mobile, even if it is "stationary". I don't know what a jolly jumper is, but I assume it requires a lot of leg movement and if he's happy in there and very active, he must have the motor skills to do things outside of it.

What you will have to do is put him on the floor and make him try. Does he roll over? Rolling is considered a form of crawling. Some babies will see something they want and instead of getting on all fours, they will just roll to the toy.

Put him on the floor and give him a toy, but put it just out of his reach....something colorful or a toy that he really loves so that he will really want it. Show it to him and see what happens. He will try to reach for it and he will know that if he goes just a little farther he can have it. He might get upset because he doesn't like being on the floor or his tummy or whatever, but that's ok....it's not going to hurt him.

He just needs to learn how to try for himself. Maybe you've been picking him up or giving him the toy or taking him to the place he needs to go instead of making him work for it.

Remember that all babies develop at different stages and that he will get there eventually. Some of it isn't because a baby can't, it's just because they never had to.....

I hope that helps. Keep me updated!