Add a license exception to single owner (Melchoir Franz and myself) that clarifies that merely calling Nasal functions from third party aircraft does not invoce the derived-work clause of the GPL. Signed of by Melchoir.

Nasal/bits.nas

@@ -1,3 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# NOTE! This copyright does *not* cover user models that use these Nasal
+# services by normal function calls - this is merely considered normal
+# use of the code, and does *not* fall under the heading of "derived
+# work."
+#
+# Copyright (C) 2008 by mfranz
+
 var bit = [var _ = 1];
 for (var i = 1; i < 32; i += 1)
 	append(bit, _ += _);

Nasal/dynamic_view.nas

@@ -1,3 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# NOTE! This copyright does *not* cover user models that use these Nasal
+# services by normal function calls - this is merely considered normal
+# use of the code, and does *not* fall under the heading of "derived
+# work."
+#
+# Copyright (C) 2006-2008 by mfranz
+
+
 # Dynamic Cockpit View manager. Tries to simulate the pilot's most likely
 # deliberate view direction. Doesn't consider forced view changes due to
 # acceleration.

Nasal/multikey.nas

@@ -1,3 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# NOTE! This copyright does *not* cover user models that use these Nasal
+# services by normal function calls - this is merely considered normal
+# use of the code, and does *not* fall under the heading of "derived
+# work."
+#
+# Copyright (C) 2008 by mfranz
+
 var translate = { 356: '<', 357: '^', 358: '>', 359: '_' };
 var listener = nil;
 var dialog = nil;

Nasal/windsock.nas

@@ -4,6 +4,14 @@
 ##
 ###############################################################################
 
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# NOTE! This copyright does *not* cover user models that use these Nasal
+# services by normal function calls - this is merely considered normal use
+# of the code, and does *not* fall under the heading of "derived work."
+#
+# Copyright (C) 2017-2020 by Erik Hofman
+
 var dt = 0.0;
 var windsock = func {
   var wind = getprop("/environment/wind-speed-kt") or 0;