Salaam alaikoum,I'm trying to make An App that displays pictures (of nature) and a button to the the social medium/website of the photographer that took the picture so that the users of the app know who took the picture. The photographers need to pay to be in the App. My question is: if people who use my app, go to the social medium/website of the photographer and they find a link to or somewhere on the website a shop and decide to buy something which is not permissible(a poster of an animatie being) although there are also permissible items. Am I to blame? (My intention is to let the user of the App know who took the picture and where you can probably follow his online work)

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

It appears – Allah The Exalted knows best- that what you have mentioned is not considered prohibited assistance, as long as the accounts that are linked to your application are not originally specialized in publishing prohibited posts, and it is not often the case, even if the account's owners display some forbidden contents in them. You are not sinful if any person uses those accounts to reach forbidden posts.

Allah Knows best.