This is the original version of DOOM Retro, v1.0, released on December 10, 2013. However, DOOM Retro's source code wasn't uploaded to GitHub until just before the release of DOOM Retro v1.1, so the correct source code for DOOM RETRO v1.0 is included in the doomretro-1.0.zip file with the binary. Visit here for the release notes.