This extension is under GPL liscense. You can view it here

By purchasing Music Collection for Joomla, you agree to be legally bound by the following terms.

1. The liscense that comes along with the purchase of Music Collection is GPL. The liscense that comes along with the purchase of Music Collection is for one live site (one live domain) only. You are allowed to install Music Collection on one (1) live site. For multiple site liscenses and support, please contact us.
2. Read the GPL liscense to be aware of your rights and terms of use.
   
3. An infringement of any of the points above will imply the cancellation of your Joomla Music Solutions account, and therefore, your access to the forum, future component updates and support.
4. The JWPlayer that is served along with Music Collection and that can be downloaded for free is LongTail Video's FREE player. You should use it under their liscense: https://www.longtailvideo.com/order/license/
   
5. Forum use must be polite. We don't allow bad behaviors, insults or SPAM. An infringement of this clause on the Forum will imply the cancellation of your Joomla Music Solutions account, and therefore, your access to the forum, future component updates and support.