I am the original author and I provided the photo for free usage, but it doesn't mean that it can be sold - https://unsplash.com/photos/KGy1GFeKBu4 The Unsplash license forbids it: https://unsplash.com/license
No, it is not allowed to use other people's assets. For being a contributor, you need to have ownership over the asset you share.
You can file a copyright claim as the owner. See the link below: