bhargavchippa also contributed to this repo, so this doesn't seem like one of those random "fork and lie" sort of thing. Without the necessary context, we can't assume much. It could well be that mwshinn was in the wrong or there was an "okay" from mwshinn for bhargavchippa to make those changes.
As I understand it, this is not permitted under the GNU General Public License v3.0. Is that correct? I would think that certain licenses do permit this (MIT possibly?). Could anybody with knowledge chime in?
MIT prohibits this. You can use the code and remix it or add your own copyrighted code, but pretty much the only thing you can’t do is remove the original copyright text.