I speak for myself, personally, but I am sure most folks will follow the same principles.

If you publicly post anything, be it code or your personal opinions, it becomes public domain. Anyone can take and do what the please with it... and they do, because I've noticed some absolutely terrible Cut & Paste examples where those involved haven't the slightest clue what they are doing! It always generates a smile when someone claims something to be their own work, but embedded is a peculiar mnemonic for a Variable or Port name that you know that you invented.

If you happen to earn a million out of it - good for you. It would be nice to get a credit (or even a crumb), but it's unlikely. After all, if it's YOUR homework, or coursework for educational credits, you're not exactly going to admit at the top of your work that it was courtesy of Darrel or Bruce and that your input was mostly boozing down the pub!

It is kinda pointless posting something publicly and then telling folks you can't use it - sure, everyone is really going to listen and respect your wishes. Many times I could have replied to a thread or posted code which would/could be of value to a competitor, or itself be of great intrinsic commercial value. I just don't post it, or if I'm feeling kind, I may just post some hints as to how to approach the solution.

So, in summary, if you post something - it becomes everyones property. If you don't like the thought of that - keep it to yourself!