Does Lightroom have a way to enter metadata information about an image, such as usage, etc., that is not exportable with the image or does not use up existing meta fields. A custom meta data box or sticky note or anything like that? If not, why not?
Yes, you can add metadata in Lightroom through the metadata panel in Library module and choose not to include it in export.
Not without a plugin. Look up my BigNote plugin which you can then extend yourself.