You cannot share the assets directly, but only projects you make using them. There is no credit necessary (as long as you don't take credit yourself or assign it to someone else, I don't mind being ignored LOL).
And that's right, there's no additional royalties. If you back on patreon you can use anything that you download from it under the same terms, commercial use for any project is fine, just don't share the assets on their own.
Thanks