EXP is based on the work of James M. Ward. Mr. Ward died on March 18th, 2024. He invented the sciency fiction RPG in the late 1970s with Metamorphosis Alpha and Gamma World. These games changed my life for the better. The News of his passing has spread slowly throughout the RPG world. The passing of this giant creative spirit is duly noted. Condolences to his family.
His official obit lies here