If there's no license, then all rights are implicitly reserved by whoever owns the copyright, probably the author, unless it was explicitly placed in the public domain.
"distributed unlicensed software (not in the public domain) is fully copyright protected, and therefore legally unusable... Examples of this are unauthorized software leaks or software projects which are placed on public software repositories like GitHub without a specified license" https://en.wikipedia.org/wiki/Software_license#Software_lice...