That's not true. Making a "new" version of something that is intentionally a copy of something else is copyright infringement. https://en.wikipedia.org/wiki/ReactOS#Internal_audit Only clean-room reverse engineering is good enough to avoid copyright claims in the US.
I'm not saying that nwienert is necessarily right or wrong, but it's strange that this post received such a strong reaction compared to the Font Awesome post.
Bootstrap is intended for use by whoever wants it. Font Awesome was presented as a tweak, an improvement. Svbtle is intended for a small audience, and Obtvse is a straight rip-off