docs

COLLABORATION_AGREEMENT.md

@@ -18,9 +18,6 @@ The MCnet guidelines developed by [www.montecarlonet.org](www.montecarlonet.org)
 are copied in [MCNET_GUIDELINES](MCNET_GUIDELINES) -- they provide a very good 
 additional scope that contributors should read and consider. 
 
-All possible
-liability and licensing question are only handled by the adopted
-software license.
 
 ## The software license of the CORSIKA project
 
@@ -29,10 +26,18 @@ license GPLv3, as copied in full in the file
 [LICENSE](LICENSE). Each source file of the CORSIKA project contains a
 short statement of the copyright and this license. Each binary or
 source code release of CORSIKA contains the file LICENSE. The
-code, documentation and content in the folder [externals](externals)
+code, documentation and content in the folder [./externals](./externals)
 is not integral part of the CORSIKA project and can be based on, or
-include, other licenses, which must be compatible with GPLv3. Check the
-content of this folder for details and additional license information. It depends on the configuration of
+include, other licenses, which must be compatible with GPLv3. 
+
+The folder [./modules](./modules) contains the code of several
+external physics models for your convenience. Please consult the
+original model authors and honor their policies and licenses. 
+Of course, we have their consent to
+distribute their code together with CORSIKA 8. 
+
+Check the content of these folders carefully for details and additional 
+license information. It depends on the configuration of
 the build system to what extend this code is used to build CORSIKA.
 
 
@@ -42,22 +47,3 @@ If you want to contribute, you need to read
 [the GUIDELINES](CONTRIBUTING.md) and comply with these rules, or help to
 improve them. 
 
-
-## The CORSIKA Projects Maintainers
-The CORSIKA Project mainters make all decisions for the CORSIKA
-Project. They can also change the
-[COLLABORATION\_AGREEMENT](COLLABORATION\_AGREEMENT.md), the
-[GUIDELINES](CONTRIBUTING.md) or any other structure or document relevant for the CORSIKA Project.
-
-The current CORSIKA Project maintainers are listed in the file [MAINTAINERS](MAINTAINERS.md). 
-
-and can be contacted via corsika-project@lists.kit.edu.  The chair
-person of the CORSIKA Project is Ralf Ulrich (KIT). Maintainers have special 
-responsibilities for specific parts of the project. 
-
-
-### Planning and performing releases
-
-The CORSIKA maintainers decide on releases of the software, and about the content of it. 
-
-

README.md

@@ -64,9 +64,9 @@ You will also need:
 - git
 - g++, gfortran, binutils, make
 
-On a bare Ubuntu 18.04, just add:
+On a bare Ubuntu 20.04, just add:
 ``` shell
-sudo apt-get install python3 python3-pip cmake g++ gfortran binutils make git 
+sudo apt-get install python3 python3-pip cmake g++ gfortran git doxygen graphviz
 ```
 
 CORSIKA 8 uses the [conan](https://conan.io/) package manager to manage our