> will encourage less diligent students to neglect their own education.
That seems like a student's issue -- not the University's. Give an in-class closed-book closed-note exam and the students who did not bother to actually learn the subject will fail.
> I stopped this practice when I got a 0 on a major bit of coursework (cost me a grade boundary in my degree...), as their software found it online, on my site, and they refused to view my work as anything but plagiarism
It seems you did not fight this hard enough. It would be easily proven it was your work and posted after you began work on the assignment. It's actually customary now at the local University by me for the professors to encourage use of Github and the like.
In the end -- the University might "own" copyright over the exact phrasing of the questions that spawned the code solutions -- but they do not own the solutions themselves.
Actively forbidding students from learning and using version control is egregious.
The argument that other students might plagiarize so all the code solutions must come down is simply ridiculous.
I'm also upset that Github redacts the contact information from the DCMA Takedown requester. Students should have an option to directly contact the individual at their University and challenge this.
There are a lot of people in this thread stating that students are not allowed to post homework solutions online and therefore this is fair -- I have never seen in any syllabus nor student conduct agreement anything forbidding posting of a student's own solutions online. A lot of student code is online - and sometimes is even used as part of their first resume after university to land their first real job.
Posting homework you did and own copyright of online is not breaking any rules. It's breaking rules to copy/plagiarize that code and attempt to pass it as your own.