My open source project was relicensed by a YC company [license updated]

An app which is build for cheating complains about cheating ...

The founders who built Glass don't complain about cheating. Rather, the developer of https://github.com/sohzm/cheating-daddy complained of copyright infringement of his code by the developers of Glass.

Worse than copyright infringement, they pretended the code was theirs

While copyright infringement is clealy legally wrong and developing general software is not, I do agree with GP that one should, morally, perhaps not complain about "cheating" the legal system when the infringed application itself is meant for cheating.

Legal correctness does not necessarily imply moral correctness.

Cheating != Stealing

Would you have the same sentiment for VPN (software built for cheating region locks) or ad blockers (software built for cheating content providers)?

They complained of license violation, not copyright infringement. There’s a big difference. The original license already granted the rights for anyone to copy the code, so the question of copyright infringement isn’t really on the table.

If you don't abide by the license terms then you don't get to copy something under the license. So breech of license means corresponding copyright infringement.

It wouldn't matter if they wrote a program to automate stealing other people's content. If you strip a GPL license off a program you redistribute, you're breaking the law.