This requires a CodeCanyon extended license which isn't turned off by default on my plugins and costs 5x the base price. You may contact me with detailed explanation of your project and where you want to use slider. If I will agree with the way how it will be redistributed and how your product looks like - I will provide the license.
For each website new regular license should be bought. Read more about regular license on CodeCanyon.
Yes, you can add as many sliders as you need to one page, with different skins, options etc.
RoyalSlider is built in best practises of WordPress plugins and works with absolutely any theme.
Check this article.
Absolutely not, RoyalSlider caches all sliders using WordPress Transients API.
Make sure that you unzipped archive that you downloaded from CodeCanyon, inside you'll find readme file.