Is there a listing of websites I can look at to see what this means and to see what others have done?
"The GPL requires that you not remove the Yendif Player logo and copyright notices from the user interface. See section 5.d below."
I take it from; the license I can upload pro version to any of my web sites?
It means, you should not remove our "Powered By" Logo by editing our source files. But, our PRO version remove this from your player. Note, that your purchase is valid for one site only. So, if you want to use in multiple sites, you need to purchase separate license for each your website.