Thank you so much for this article, it helped me a lot to get some things clear and to google for the right keywords :)
The only thing I don't quite get is the fact that under the first picture (with all the standards) it says: "No attribution required" - As you wrote yourself, for example in CC BY you HAVE TO attribute. As far as I understood the whole topic you don't have to attribute if the source for example says:

• The pictures are free for personal and even for commercial use.
• You can modify, copy and distribute the photos.
• All without asking for permission or setting a link to the source. So, attribution is not required.

For CC BY and all the combinations it says:

You must give appropriate credit, provide a link to the license...

What am I getting wrong or is the picture caption wrong?

Greetings,
Marla

Edit: Okay, I guess the picture caption is a caption that doesn't refer to the standards/licences shown in the picture.
Got it ;) It simply states that this given picture doesn't need attribution ;)