If you teach, preach, or reach anyone online—what are your copyright issues?
When I was a permissions editor in the 1980s, someone trademarked the phrase “three-peat” (three consecutive wins). Maybe I owe someone money for even using the phrase in this article. Or maybe not.
Some years later, publishers tried to assert that there was no such thing as copyright on the Internet. That was a huge rights grab on their part because they asserted it among themselves while denying it to writers.
In fairness, they may have been just as confused as everyone else was, in the Nineties, about issues like that. Writers successfully resisted them, but where are we now?
The Internet changed a lot of things. On the one hand, the Internet makes it easier than ever to detect plagiarism. On the other hand, comedians claim that people are stealing their jokes. Possibly, jokes are the easiest thing to steal. Over coffee. To make a point. But before the era of the blog, the theft would hardly be pursuable.
Right now, it is a frontier, so one can only assert general principles:
Copyright law still governs, but it takes time to change laws to conform to reasonable principles . For example, as one library group asserts re new media

Many people assume that everything posted on the Internet is public domain, probably because our law used to protect published works only if they displayed the proper copyright notice upon publication. The law, however, has changed: neither publication nor a notice of any kind is required to protect works today. Simply putting the pen to the paper or in the electronic medium, putting the fingers to the save key creates a copyrighted work. Once expression is committed to a tangible medium (and computer media is considered tangible), copyright protection is automatic. So, postings of all kinds are protected the same as published printed works.

But that doesn’t really make sense. Some postings are as informal as a remark over coffee, others are as formal as a novel or a Constitution.
Here is a possibly useful primer on "copymyths" today, that fleshes out some of the legal issues:

1) "If it doesn't have a copyright notice, it's not copyrighted."

This was true in the past, but today almost all major nations follow the Berne copyright convention. For example, in the USA, almost everything created privately and originally after April 1, 1989 is copyrighted and protected whether it has a notice or not. The default you should assume for other people's works is that they are copyrighted and may not be copied unless you know otherwise. There are some old works that lost protection without notice, but frankly you should not risk it unless you know for sure.

I will try to post more on this, as it is definitely a developing area. It obviously matters if you are a teacher, for example. However, one cannot copyright ideas, so one solution is possibly to paraphrase an idea in one’s own words, crediting the source. Imitation is still the sincerest form of flattery. Next: How has the Internet affected claims about defamation? How has it affected claims about blasphemy? Denyse O’Leary is a Canadian journalist, author, and blogger.