This would be a second plugin that happens to share a lot of the same code with the Kobo Touch Extended driver. My recommendation for people using it, unless Kobo gives me their KePub generation code, would be to not delete their ePub (or whatever other format) copies of any KePub books.
Although I'm not sure it's fair to call KePub entirely proprietary. Kobo's use of it definitely is, but I see no reason why any compliant ePub reader couldn't make full use of a properly created KePub file. That "properly created" bit being the key reason I would strongly recommend having some other format as your backup copy of course
