> ...there is nothing to lose in challenging the complaint.

Are you sure? See GitHub's DMCA counter notice policy[1], specifically, item 3:

> Provide your contact information. Include your email address, name, telephone number, and physical address.

In other words, without paying to retain legal counsel, this guy would have to expose his personal identifiable information (surrendering anonymity) to an unethical, ruthless pack of legal professionals to restore the repo and live with the looming threat of all sorts of perfectly legal harassment.

[1] https://help.github.com/en/github/site-policy/guide-to-submi...