As I recollect, Don H., you are right. I was working for an intellectual property lawyer while studying technical writing in college. I recall some of the things he said about copyright that follow the same line of thought you seem to have above.
I recall a few others things, one in particular that might shed some light on the controversy over copyrighting a lesson plan as distinguished from the lesson content. According to Tom Freiburg, a patent and trademark attorney here in San Francisco, any sequence of 6 or more words is copyrightable, which means to my understanding that the lesson plan, in the sense that the words/graphics are arranged in a certain order, is part of the copyright.
One concern! I also read within this thread about using someone else's work. From my readings on various copyright websites
you can quote another's works and attribute those works providing they fall within fair use rules. These rules contain a lot of grey areas, so it is always best to get written permission to use the quoted content within the lesson plan.
Lastly, as you say, once you publish the lesson plan on the web, it automatically is copyrighted; however, few systems that I know of log more than the mere fact that you published something on a certain day at a certain time. As such, formally copyrighting the material (lesson plan) has its merits. Unless the file (lesson plan) somehow gets deleted from your server
, that file is labeled in the log. So as long as you can open the lesson plan from the server, it's copyrighted (i.e. you have a way of showing that you are the originator of that content on that day and time as shown by the file and the log. Only someone who can show that they originated the lesson plan before that can claim copyright ownership, but they can do that even if you file a copyright. So...
I once liked a poem so much that I rewrote it with completely different content. I used the rhyme but I changed the content of the poem to express the thoughts I loved then, editing. I made sure that no sequence of original content existed beyond 5 words. So, I could copyright the poem. In other words, I think your lesson plan is safe so long as the file is logged onto the server.