@kus_kus. Thanks for posting your questions. I will answer them as best as I can:
1) The license type is found in the “Terms of Use” at the bottom of every webpage: https://www.valorapps.com/terms-of-use.html. Basically, all the Joomla extensions that I produce are licensed as GPL. This is a requirement of JED that I have to abide by. There is a link to the license on the product page itself, so I am not sure how you missed it. Basically, it is a one-time payment, unless I release a new major version. You can use it on as many sites as you like. I don’t have any restrictions. You can have a look at my upgrade policy.
2) I do have ACL implemeneted. So, you can specify the access levels for each file or listing, whether it is Public, Registered, Special or whatever you create. To be honest, I am not too sure what you mean by “change access rights per different groups of groups”.
3) Yes, direct links to files are hidden. Please look at the demo for a preview.
Hope my answers have helped you.