if you decide to update this more, then modifying the gridlauncher one "should" be pretty simple. you do need to host the .php scripts somewhere though, and set it up with Github webhooks.I guess I would be able to edit gridlauncher's updater, but it uses lua and some http, which I'm not really familiar with.
it's currently set up to fit the gridlauncher's situation, such as the version number and having a changelog as a .md file. if you decide to not use this changelog, it can be disabled but it's not like changing something from "true" to "false" (yet).
yeah it's not exactly portable, though I might do this closer to the day my site hosting expires, which is around June 2016. I can definitely make a customized one though, or help with it.