The $libraries object is a general object with no purpose other than to be the parent for all code library objects. Code library objects should be primarily focused as single-method utilities (objects which have a single purpose as a whole should be parented to $utilities).
Generally speaking, libraries should all have a _lib suffix, unless they are a library for a data type.
Colors | Trie | List Library | has_text | mutex | Heap | Weather System | Math Library | Integer | Data Lib | Object Lib | Help Node | Code Lib | Generic Map | Scrabble | World Time | Time | Robot | Native Function Reference | Complex Number Library | Bytecode Docs | motd | Mail List | Float | Collective | libraries | social_ui