Update README.md

README.md

-4C open source publication
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+README 4C - FORSEE - FORESt Ecosystems in a changing Environment
+
+This file contains basic information on the open source distribution of
+the computer simulation model 4C. The model has been developed and is maintained
+at the Potsdam Institute for Climate Impact Research (PIK) in Potsdam, Germany,
+see "opensource_PIK_approval".
+
+All source code and documents provided are subject to copyright (c) by the 
+Potsdam Institute for Climate Impact Research. All files are licenced under 
+BSD 2-Clause License, see the LICENCE file for details. The 4C model is a 
+collaborative work, see the AUTHOR file for details.
+
+For a basic introduction and installation see the file .... 
+For manual on "how to start" see the directory manuals. 
+For background information documents see the directory description/additional. 
+To test the propper working of the functions of the model see the directory data/4C testing. 
+All relevant publications regarding the model see the directory publications.
+
+The source code is distributed via a git repository at: 
+https://gitlab.pik-potsdam.de/foresee/4C
+The code language is Fortran and is ready to use. Since the model development is
+finished, there is no further development and no further support in model 
+download, setup, development or application. No merge or other development 
+requests will be handeled. There fore there are no code style recommendations or
+instructions on how to create source code ammendments.
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