Remember
Ultimately you are responsible for checking the copyright of material you use.
If you want to use some material and can not 'see' the licence you can always ask for permission!
If in doubt of 'fair use' any material, you should contact the copyright owner.
Always check the ownership and sharing rights at a web site as things may change.
If linking, embedding and sharing is allowed at the site then you are able to do those things without asking. E.g most youtube videos allow embedding.
The only thing you can guarantee about the Internet is that things will change..........