I didn’t make these, Garry stopped including them in the Mac and Linux versions of Garry’s Mod back before Steampipe (Missing gmad/gmpublish on OS X · Issue #276 · Facepunch/garrysmod-issues · GitHub). They work fine, I periodically use them to package addons for the workshop and extract addons for my TTT server.
(Couldn’t find the Linux version(s), will update when found.)
http://forum.facepunch.com/showthread.php?t=1244179 - GMPublish
http://www.facepunch.com/showthread.php?t=1242185 - GMad