Bob et el,
Let me add a caveat; I am NOT a lawyer, I have no legal training. I am NOT an expert on copyright law. I have been involved with the copyright issues for 30+ years. I have sued, and won a copyright violation lawsuit. I have stopped the illegal usage of my copyrighted material on several occasions. That said.
The problem with stuff that you obtained off the internet, in most cases is that a lot of the stuff was put there without the knowledge or permission of the copyright owner. Most of the time it’s used under the incorrect assumption that “it’s all right to do so”, do to their ignorance of the laws, in most cases from someone making assumptions, not based on fact.
If one was to read the copyright laws there IS an “exception” for educational use. BUT, it’s legal usage is spelled out very plainly, is in fact, rather restrictive, and still requires proper crediting of the materials owner.
Purchasing an item, that is protected under the copyright laws ( and almost everything is), only gives you the right to use that item, as intended by the copyright owner. You buy an item, not the rights to go with that item.
As a train example: You buy a ( one ) part from a “Third Party” supplier. Wow its great just what you needed. You bought it paid good money for it, and it yours. You want several more, so it’s easy, you make a mold and cast some more, “It’s OK cause I’m only making a few for myself and not selling them”. Giving a few more to your buddies is “OK cause I’m not selling them or making a profit”. WRONG ON ALL ACCOUNTS! Making a copy of someones copyrighted item even for your own usage is illegal! Giving them away is also illegal
We will not even get into the MORAL or ethical issues!
Bottom line… If you did not create it, ask permission before using it. Including making copies of it