The GPL3 license provide right to share. modify and use for any purpose including commercial or noncommercial and only and only accepts dual license if they are compatible, a closed license or as you call 'commercial' are not compatible, GPL3 only supports 'libre/open' licenses.
Does the license you call 'commercial' is open/libre? in README.md says it's GPL3 but the file specified LICENSE.md not see this text -> http://www.gnu.org/copyleft/gpl.html
The GPL3 license provide right to share. modify and use for any purpose including commercial or noncommercial and only and only accepts dual license if they are compatible, a closed license or as you call 'commercial' are not compatible, GPL3 only supports 'libre/open' licenses.
Does the license you call 'commercial' is open/libre? in README.md says it's GPL3 but the file specified LICENSE.md not see this text -> http://www.gnu.org/copyleft/gpl.html