Well I have been doing a little studying on this. I can't seem to find anything that hints at the fact that it would make good bow wood. Ginkgo is described as being a light, fine grained , yellowish, flexible wood. It has been used to make cutting boards, rice bowls, ornate carvings, etc. No mention of bows or it's abilty to withstand stresses. However It has been planted near temples to protect them from fire. It is naturally insect resistant. It is believed to have natural fire supression qualities. It holds up to ice and snow. (I can attest to the fact that my neighbor's tree has never shed a broken branch) This is in addition to all of it's medicinal qualities. It was the one species of tree that withstood the atomic bomb at Hiroshima, then recovered and thrived! Surviving trees from that horrific event are still around today!
That said, I would split some, dry it out until it stops losing weight, then see how it holds up to bow work!