The RibbonLib is part of the bigger MapBasic Common Libraries. You can find it via the Community Download page: goo.gl/Lh5hrH.
But I would recommend that you get it directly from Github as you here will get the most up-to-date version of the libraries: https://goo.gl/leKoI0
![mbLibrary Github]()
From Github you can either download a zip-file with the entire MapBasic Common Libraries or you can use Git to clone the repository to your desktop. That makes it easier to get changes to the libraries later on.