Wildpants is the core engine behind Bagnon and Bagnonium. Having a shared codebase allows for easier maintenance and for new features to be simultaneously implemented on both addons without additional effort.
It is not a library to be reused to implement other addons, as it constitutes the vast majority of what these addons are. Bagnon and Bagnonium are just two different skins implemented over the engine.
Are you a developer? Wildpants provides a rich API for developing plugins or addons that interact with Bagnon and Bagnonium: