You only need to worry about the "Limited License Material." In which case, you have to read the "broken" English very carefully, it will tell you restrictions right on the main page of the asset.
Aside from that, all the others have a "Free" tag. You can use them in your own works for free without any copyright infringement, and the uploaders are obligated to make sure their uploads are original and aren't causing infringement issues either.
Just don't try to modify or redistribute the assets by themselves, that is all.
Again, it's free to use in your own creative works unless it explicitly says so on the main page of the asset, don't modify or distribute assets themselves.