They are derivative from RMMV generator assets, so you need an RPGMakerMV license to use then. No other conditions required.
If you already have additional assets in your generator, you may need to change the numbers of all the assets to not overwrite your own.
To install, unzip it and copy the Generator folder in your RMMV folder. The game engine, not your game project.
The pack contain the bunny ears, tail and loving winking eyes.