LookingGlass's name is a reference to Through the Looking Glass (The novel following Alice in Wonderland).
The mod provides an API for other mods to use to create live, animateable render views of other dimensions. It does all the heavy lifting and rendering of the other worlds, providing a simple interface to the perspective of the other world. The rendering of the other world is provided as a simple texture.
LookingGlass may be included in mod packs at will. No direct permissions are necessary. A list of mods, their authors, and the permission information must be made available for your pack, however.