i have alot paid add-ons some coders expert but not smart some coders are really greedy i have 5-6 paid add ons from same coder and i have still his web page advertising link.
From now on i will not review about add ons if producer wanna my review they have to pay for this thank who care this post.
The add-on description should state whether there is a copyright link or not.
In most cases additional payment can be made to remove it.
It is up to the purchased to carry out due diligence and ensure the add-on meets their requirements before purchasing.
If it doesn't you can post on the thread with your questions and concerns or contact the developer directly.
Having said that, the rating and review ratio is very low for resources, sadly.