Maratis is an open source game development tool designed for artists and developers. It’s developed by Anaël Seghezzi.
“After years of hard work and a rather lonely journey,” Seghezzi said, “I’m proud to present the first-release candidate of Maratis. I believe that Maratis will be invaluable to professionals and students alike, and will respond perceptively to their most primary concern–creation.”
There are screenshots available here. You can download Maratis here.