Update Packaging/nix/devilutionx.6

update COPYRIGHT section

Author: krekhovx

Packaging/nix/devilutionx.6

@@ -129,10 +129,12 @@ Changelog:
 .SH AUTHOR
 Written by the DevilutionX community.
 .SH COPYRIGHT
-This software is being released to the Public Domain. No assets of Diablo are being provided. You must own a copy of Diablo and have access to the assets beforehand in order to use this software.
+DevilutionX is made publicly available and released under the Sustainable Use License (see LICENSE).
+
+.B https://github.com/diasurgical/DevilutionX/blob/master/LICENSE.md
 .P
-Battle.net® - Copyright © 1996 Blizzard Entertainment, Inc. All rights reserved. Battle.net and Blizzard Entertainment are trademarks or registered trademarks of Blizzard Entertainment, Inc. in the U.S. and/or other countries.
+The source code in this repository is for non-commercial use only. If you use the source code, you may not charge others for access to it or any derivative work thereof.
 .P
 Diablo® - Copyright © 1996 Blizzard Entertainment, Inc. All rights reserved. Diablo and Blizzard Entertainment are trademarks or registered trademarks of Blizzard Entertainment, Inc. in the U.S. and/or other countries.
 .P
-This software is in no way associated with or endorsed by Blizzard Entertainment®.
+DevilutionX and any of its maintainers are in no way associated with or endorsed by Blizzard Entertainment®.