Clarify licensing status

This follows up on a suggestion by James Knight in:
http://mm.icann.org/pipermail/tz/2015-October/022799.html
* .gitignore, CONTRIBUTING, Makefile, README, checklinks.awk:
* checktab.awk, tzselect.ksh: Mention that they’re public domain.
* LICENSE: New file.
* Makefile (COMMON): Add it.
* NEWS: Document this.
* date.c, newstrftime.3, strftime.c: Switch to 3-clause BSD license.

.gitignore

@@ -1,3 +1,5 @@
+# Files intentionally not tracked by Git.
+# This file is in the public domain.
 *.a
 *.asc
 *.o

CONTRIBUTING

@@ -67,3 +67,7 @@ Git repository.  If you use Git the following workflow may be helpful:
 Please do not create issues or pull requests on GitHub, as the
 proper procedure for proposing and distributing patches is via
 email as illustrated above.
+
+-----
+
+This file is in the public domain.

LICENSE

@@ -0,0 +1,4 @@
+With a few exceptions, all files in the tz code and data (including
+this one) are in the public domain.  The exceptions are tzcode's
+date.c, newstrftime.3, and strftime.c, which contain material derived
+from BSD and which use the BSD 3-clause license.

Makefile

@@ -344,7 +344,7 @@ MANTXTS=	newctime.3.txt newstrftime.3.txt newtzset.3.txt \
 			time2posix.3.txt \
 			tzfile.5.txt tzselect.8.txt zic.8.txt zdump.8.txt \
 			date.1.txt
-COMMON=		CONTRIBUTING Makefile NEWS README Theory
+COMMON=		CONTRIBUTING LICENSE Makefile NEWS README Theory
 WEB_PAGES=	tz-art.htm tz-link.htm
 DOCS=		$(MANS) date.1 $(MANTXTS) $(WEB_PAGES)
 PRIMARY_YDATA=	africa antarctica asia australasia \

NEWS

@@ -22,6 +22,11 @@ Unreleased, experimental changes
 
   Changes affecting documentation
 
+    A new file LICENSE makes it easier to see that the code and data
+    are mostly public-domain.  (Thanks to James Knight.)  The three
+    non-public-domain files now use the current (3-clause) BSD license
+    instead of older versions of that license.
+
     tz-link.htm mentions the BDE library (thanks to Andrew Paprocki)
     and CCTZ (thanks to Tim Parenti).
 

README

@@ -10,10 +10,6 @@ locations around the globe.  It is updated periodically to reflect
 changes made by political bodies to time zone boundaries, UTC offsets,
 and daylight-saving rules.
 
-Unless otherwise specified, all files in the tz code and data are in
-the public domain, so clarified as of 2009-05-17 by Arthur David Olson.
-The few exceptions are code derived from BSD, which uses the BSD license.
-
 Here is a recipe for acquiring, building, installing, and testing the
 tz distribution on a GNU/Linux or similar host.
 
@@ -59,3 +55,9 @@ None of them are responsible for remaining errors.
 Look in <ftp://ftp.iana.org/tz/releases/> for updated versions of these files.
 
 Please send comments or information to tz@iana.org.
+
+-----
+
+This file is in the public domain, so clarified as of 2009-05-17 by
+Arthur David Olson.  The other files in this distribution are either
+public domain or BSD licensed; see the file LICENSE for details.

checklinks.awk

@@ -1,6 +1,6 @@
 # Check links in tz tables.
 
-# Contributed by Paul Eggert.
+# Contributed by Paul Eggert.  This file is in the public domain.
 
 BEGIN {
     # Special marker indicating that the name is defined as a Zone.

checktab.awk

@@ -1,6 +1,6 @@
 # Check tz tables for consistency.
 
-# Contributed by Paul Eggert.
+# Contributed by Paul Eggert.  This file is in the public domain.
 
 BEGIN {
 	FS = "\t"

date.c

@@ -1,19 +1,31 @@
-/*
- * Copyright (c) 1985, 1987, 1988 The Regents of the University of California.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms are permitted
- * provided that the above copyright notice and this paragraph are
- * duplicated in all such forms and that any documentation,
- * advertising materials, and other materials related to such
- * distribution and use acknowledge that the software was developed
- * by the University of California, Berkeley.  The name of the
- * University may not be used to endorse or promote products derived
- * from this software without specific prior written permission.
- * THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
- */
+/* Display or set the current time and date.  */
+
+/* Copyright 1985, 1987, 1988 The Regents of the University of California.
+   All rights reserved.
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+   3. Neither the name of the University nor the names of its contributors
+      may be used to endorse or promote products derived from this software
+      without specific prior written permission.
+
+   THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS" AND
+   ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+   ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+   FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+   OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+   OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+   SUCH DAMAGE.  */
 
 #include "private.h"
 #include "locale.h"

newstrftime.3

@@ -14,11 +14,7 @@
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
-.\" 3. All advertising materials mentioning features or use of this software
-.\"    must display the following acknowledgement:
-.\"	This product includes software developed by the University of
-.\"	California, Berkeley and its contributors.
-.\" 4. Neither the name of the University nor the names of its contributors
+.\" 3. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"

strftime.c

@@ -1,29 +1,40 @@
+/* Convert a broken-down time stamp to a string.  */
+
+/* Copyright 1989 The Regents of the University of California.
+   All rights reserved.
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+   3. Neither the name of the University nor the names of its contributors
+      may be used to endorse or promote products derived from this software
+      without specific prior written permission.
+
+   THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS" AND
+   ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+   ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+   FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+   OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+   OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+   SUCH DAMAGE.  */
+
 /*
-** Based on the UCB version with the copyright notice and sccsid
-** appearing below.
+** Based on the UCB version with the copyright notice appearing above.
 **
 ** This is ANSIish only when "multibyte character == plain character".
 */
 
 #include "private.h"
 
-/*
-** Copyright (c) 1989 The Regents of the University of California.
-** All rights reserved.
-**
-** Redistribution and use in source and binary forms are permitted
-** provided that the above copyright notice and this paragraph are
-** duplicated in all such forms and that any documentation,
-** advertising materials, and other materials related to such
-** distribution and use acknowledge that the software was developed
-** by the University of California, Berkeley. The name of the
-** University may not be used to endorse or promote products derived
-** from this software without specific prior written permission.
-** THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
-** IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
-** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
-*/
-
 #include "tzfile.h"
 #include "fcntl.h"
 #include "locale.h"

tzselect.ksh

@@ -7,7 +7,7 @@ REPORT_BUGS_TO=tz@iana.org
 # Ask the user about the time zone, and output the resulting TZ value to stdout.
 # Interact with the user via stderr and stdin.
 
-# Contributed by Paul Eggert.
+# Contributed by Paul Eggert.  This file is in the public domain.
 
 # Porting notes:
 #