“All you have to do is to put the attribution in the credits.” – this is not trade-free.

They have some trackers or even ads on their website. Plus, when you download you are faced with a popupu asking you to follow them on social networks (that are trade-based) and/or donate to them. it is a bit pushy and they want your attention a bit. They also offer some music for a price. So they are barely trade-free if at all. They also sell some subscriptions.