update readme

README.txt

-Minetest Game [minetest_game]
-=============================
-The main subgame for the Minetest engine
-========================================
-
-To use this subgame with the Minetest engine, insert this repository as
-	/games/minetest_game
-
-The Minetest engine can be found in:
-	https://github.com/minetest/minetest/
-
-Compatibility
---------------
-The Minetest Game github master HEAD is generally compatible with the github
-master HEAD of the Minetest engine.
-
-Additionally, when the Minetest engine is tagged to be a certain version (eg.
-0.4.10), Minetest Game is tagged with the version too.
-
-When stable releases are made, Minetest Game is packaged and made available in
-	http://minetest.net/download
-and in case the repository has grown too much, it may be reset. In that sense,
-this is not a "real" git repository. (Package maintainers please note!)
-
-License of source code
-----------------------
-Copyright (C) 2010-2012 celeron55, Perttu Ahola <celeron55@gmail.com>
-See README.txt in each mod directory for information about other authors.
-
-This program is free software; you can redistribute it and/or modify
-it under the terms of the GNU Lesser General Public License as published by
-the Free Software Foundation; either version 2.1 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU Lesser General Public License for more details.
-
-You should have received a copy of the GNU Lesser General Public License along
-with this program; if not, write to the Free Software Foundation, Inc.,
-51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
-
-License of media (textures and sounds)
---------------------------------------
-Copyright (C) 2010-2012 celeron55, Perttu Ahola <celeron55@gmail.com>
-See README.txt in each mod directory for information about other authors.
-
-Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)
-http://creativecommons.org/licenses/by-sa/3.0/
-
-License of menu/header.png
-Copyright (C) 2015 paramat CC BY-SA 3.0

readme.md

+#### Minetest Game [minetest_game]
+
+The main subgame for the Minetest engine
+
+##### Caution: this repository contains modifications for the [illuna-minetest.tk](//illuna-minetest.tk) Minetestserver.
+
+Please **don't use** this subgame for your production environment.
+* [to the original minetest_game](https://github.com/minetest/minetest_game)