Need help defining a custom license

Hello all,

math/add have a license included in tarball that I'd like to define it in
Makefile.
Any help is welcome!

COPYING:
---
$Id: COPYING,v 1.11 2023/02/05 13:28:41 tom Exp $

ADD

--------------------------------------------------------------------------------

Copyright 1995-2022,2023 by Thomas E. Dickey.  All Rights Reserved.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name of the above listed copyright holder(s)
not be used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

THE ABOVE LISTED COPYRIGHT HOLDER(S) DISCLAIM ALL WARRANTIES WITH REGARD
TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
---

Thanks,
-- 
Nuno Teixeira
FreeBSD Committer (ports)