I'm writing a hiking guidebook and am hoping to adapt versions of maps created by a member called "John_M." The maps are from "NE USA Topo Part 1." I'd be happy to cite his name and to say something like "Adapted from NE USA Topo Part 1 maps by [his name]. Used with permission." I've asked the GPS FileDepot people to contact him on my behalf, but in case I don't hear back, does anyone know what the copyright situation is with these maps? I'd appreciate any advice. I'm adding lots of things and deleting lots of things, so they are quite different from the original, but I just want to make sure it's okay to adapt these maps. Thanks!