I sent him an email. If more people do this, it may be fixed sooner.
Here is the email I sent him:
>Thank you for carrying on the development of Screengrab.
>I noticed that there is no license included on the project page, or in the
source code of Screengrab (fix version).
>The original Screengrab code is licensed under the GNU General Public
License version 3, which I attached to this email. A requirement of the GNU
GPL is that all derivatives must be under the same license, and the licensing
has apparently been removed. In order to make the addon GPL-compliant, you
must change the license to the GPL version 3.
>The FSF Licensing & Compliance Lab:
>http://www.fsf.org/licensing
