add attribution

Author: emerbitz

README.md

@@ -7,10 +7,13 @@
 GROMACS topology files for python
 
 ## Description
-The package gmx-top4py provides an python interface to
+The `gmx-top4py` project provides a python interface to
 * read and write toplogy and force field information from GROMACS-type top-files
 * alter force field parameters 
 
+The `gmx-top4py` project derives this functionality from the [kimmdy](https://github.com/graeter-group/kimmdy) project, originally developed by the graeter-group, and includes only minor modifications to parts of the original code to operate independently.
+The `kimmdy` project is licensed under the [GNU General Public License v3.0](https://www.gnu.org/licenses/gpl-3.0.html) and, as a derivative work, the `gmx-top4py` project is distributed under the same license.
+
 ## Tutorials
 The following tutorials are avaiable as Google Colab notebooks and hence do not require a local installation:
 * [Basic tutorial](https://colab.research.google.com/drive/19zjIw2H5O6InLDQWLXEvrwrZ5w0AL7i1?usp=sharing) - Basic accessing of topology information with gmx-top4py