In order for UltralightUE to access user-defined assets for use in rendering, and actually using the library, there needs to be an interface that allows developers to access to define paths, or package files(*.pak) to pass to the plugin for resource access.
For developers that choose to package ultralight assets into paks, there are required resources for the application to withhold, like:
resources ("resources.pak") This package MUST be generated by the developer. it should contain the resource package containing the .dat, and the certification file that was included with the plugin. NO MAIN RESOURCES SHOULD BE STORED HERE, THE PLUGIN WILL REFUSE/NOT READ ANY OTHER FILES.
inspector ("inspector_resources.pak") This is optional, and not really recommended for release, but it is possible for the developer to store inspector assets here. the plugin doesn't care what extra assets are stored within this package, but it will require the actual inspector assets to be contained.