This is a hexmap version J.D. Neal’s Chaotic Caves map from his The Chaotic Caves supplement for Basic Fantasy, released under the OGL, which is basically a nice, simple, hexcrawl retroclone of The Keep on the Borderlands. C.R. Brandon released a version reskinned for Heroes & Other Worlds. Since I was kind of irritated by the square grid in the map, I ripped it out and replaced it with a hex grid to approximately the same scale (1 hex = 1 mile, instead of 1 square = 1 mile). If I have energy I might even go as far a coloring it, though even doing this much took way more time than I had hoped. (If there’s a truly easy way to just lay down a hex grid in GIMP, I couldn’t find it. The otherwise nice hexGIMP plugin I found assumed that you wanted to hand-place all the hexes… and Hexographer has pretty much the same assumption: you can import an image to trace over it, but just imposing a simple hex grid of a particular size? Forget about it. I ended up just creating custom graph paper at the right scale and combining the images in Paint.NET, having had my fill of GIMP for the evening.)
You can get the free PDF version of the Basic Fantasy edition of The Chaotic Caves here. The HOW pdf version is available from C.R. Brandon’s Lulu store (and is somewhat inexplicably more expensive than the print version of the BF edition on Amazon, but it does save you any headaches converting from D&D to HOW).
Anyway, enjoy! Naturally, this version of the map is also released as OGL-licensed, but if you think I’m going to add the complete text of the OGL itself to the image, fuggedaboutit.