Add GPL rider that prohibits GitHub hosting

[pombredanne]

See https://thelig.ht/code/dbxfs/file/LICENSE.html via @pabs3

dbxfs is generally licensed under the GPLv3+. Additionally it has the
restriction that this code cannot be hosted on GitHub. In the instance
where the prohibition of hosting this code on GitHub conflicts with
the text of the GPLv3+, the prohibition of hosting this code on GitHub
takes precedence.

Note that a license notice is not code, therefore I think it is OK to host the license notice here for detection purpose, but I am reaching out to the author to ask for permission

[pombredanne]

I sent this email to @rianhunter

From: Philippe Ombredanne pombredanne@nexb.com
Date: Wed, Jul 31, 2024 at 3:47 PM
Subject: Your license text for dbxfs
To: Rian Hunter rian@alum.mit.edu
Cc: Ayan Mahapatra asmahapatra@nexb.com
Hi Rian:
Ayan and I maintain a license detection tool called ScanCode.
Is it OK to keep a copy of your license text at
https://thelig.ht/code/dbxfs/file/LICENSE.html in our license database
we use for detection?
Without this, we cannot detect it, and cannot help folks to comply
with your terms.
This is in reference to #3879
Cordially
Philippe Ombredanne