BTW, the author has done this, committed an hour ago. The "github.com/apexskier/cryptoPadding" dependency is removed, padBuffer() and unpadBuffer() functions which look very different than apexskier/cryptoPadding are inlined. He also added tests for the padding! Nice work!
Dang, I was going to try to refute you by saying no license meant no restrictions, but nope! Creators of software (and any written work apparently [1]) are automatically granted copyright for their work (this makes sense) so without a license, copying it would be a violation of copyright. That's wild, but seems reasonable.
Posting it to Github isn't implicit permission, but it would probably be a factor if the author did try to sue people for using his or her copyrighted work without license/permission.
There's also apparently terms in the Github ToS that allow viewing and forking of public projects regardless of license. What this means in a practical sense, I'm not sure.
It's pretty simple. In a practical sense it means that the author of any license-free project on Github who finds their code used in other software can, very cheaply, C&D the authors of those packages.
https://github.com/apexskier/cryptoPadding/blob/master/pkcs7...
I think it would be a good idea to avoid that otherwise small dependency with some copy-pasta/vendoring.