Perhaps the people who spent a lot of time and money to produce the websites.....and who own copyright ...don't want anybody using their work without payment or credits. Have you contacted the websites owners to ask permission?
IF any person(s) use anything from websites without permission apart from being to lazy to email to request permission....could face a legal action if and when the sites owners fins out.
There is another her misconception that "free" websites and content on "social media" such as the dreaded FaceBook....can be used without consequence. Almost all "free" websites are common licence material - which requires permission and those who give permission do so only for personal or none profit reproduction.
i Use a blocking script on my websites which apart from preventing a right click...those who try are whisked off my website to the the UK copyright website page which explains my rights!
You may wish to check out your iBooks contract with Apple and read their warnings on use of others copyright material.
You could ..and should contact the websites...explain what you want to use and why....and ask them if they can supply media.