The package contains libraries we share between several our add-ons. Until now the files were included in packages of the add-ons themselves, however, having multiple add-ons to using the same files can sometimes cause a conflict between them, if they are using different versions of the files.
The package does not implement any visible functionality itself, it is just a collection of PHP classes reused by multiple add-ons. You don't need to install it if you are not using any of their add-ons.