Updating the README.md to point to the file USING_COLLABORATING.md (renamed...

Updating the README.md to point to the file USING_COLLABORATING.md (renamed and adapted from COLLABORATION_AGREEMENT.md). Add a file in the FLUKA directory pointing to their website for license, mentioning the desired reference and the request to register in case people are using a version with binary enclosed. Changes from GPL to BSD in README.md and USING_COLLABORATING.md to be made in another merge request.

README.md

 # CORSIKA 8 Framework for Particle Cascades in Astroparticle Physics
 
-The purpose of CORSIKA is to simulate any particle cascades in
-astroparticle physics or astrophysical context. A lot of emphasis is
+The purpose of CORSIKA 8 is to simulate any particle cascades in
+astroparticle physics or astrophysical context. A lot of emphasis has been
 put on modularity, flexibility, completeness, validation and
-correctness. To boost computational efficiency different techniques
+correctness. To boost computational efficiency, different techniques
 are provided, like thinning or cascade equations. The aim is that
-CORSIKA remains the most comprehensive framework for simulating
+CORSIKA 8 remains the most comprehensive framework for simulating
 particle cascades with stochastic and continuous processes.
 
 The software makes extensive use of static design patterns and
 compiler optimization. Thus, the most fundamental configuration
-decision of the user must be performed at compile time. At run time
+decisions of the user must be performed at compile time. At run time,
 model parameters can still be changed.
 
 CORSIKA 8 is by default released under the GPLv3 license. See [license
@@ -19,31 +19,36 @@ which is part of every release and the source code.
 
 If you use, or want to refer to, CORSIKA 8 please cite ["Towards a Next
 Generation of CORSIKA: A Framework for the Simulation of Particle
-Cascades in Astroparticle Physics", Comput.Softw.Big Sci. 3 (2019)
-2](https://doi.org/10.1007/s41781-018-0013-0). We kindly ask (and
-require) any relevant improvement or addition to be offered or
+Cascades in Astroparticle Physics", Comput. Softw. Big Sci. 3 (2019)
+2](https://doi.org/10.1007/s41781-018-0013-0) as well as
+["Simulating radio emission from particle cascades with CORSIKA 8", Astropart. Phys. 166 (2025)
+103072](https://doi.org/10.1016/j.astropartphys.2024.103072).
+
+We kindly ask (and require) any relevant improvement or addition to be offered or
 contributed to the main CORSIKA 8 repository for the benefit of the
 whole community.
 
-When you plan to contribute to CORSIKA 8 check the guidelines outlined here:
+CORSIKA 8 makes use of various third-party code, in particular interaction
+models. Please check the [using and collaborating
+agreement](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/USING_COLLABORATING.md)
+for further information on this topic.
+
+If you plan to contribute to CORSIKA 8, please check the guidelines outlined here:
 [coding
 guidelines](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/CONTRIBUTING.md). Code
-that fails the review by the CORSIKA author group must be improved
+that fails the review by the CORSIKA 8 author group must be improved
 before it can be merged in the official code base. After your code has
 been accepted and merged, you become a contributor of the CORSIKA 8
 project (code author).
 
-IMPORTANT: Before you contribute, you need to read and agree to the
-[collaboration
-agreement](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/COLLABORATION_AGREEMENT.md). The agreement can be discussed, and eventually improved.
-
-We also want to point you to the [MCnet
-guidelines](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/MCNET_GUIDELINES), which are very useful also for us.
+IMPORTANT: Before you contribute, you need to read and agree to the conditions set out in the
+[using and collaborating
+agreement](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/blob/master/USING_COLLABORATING.md).
+The agreement can be discussed, and eventually improved if necessary.
 
 
 ## Get in contact
   * Join our chat threads using Mattermost via this [invite link](https://mattermost.hzdr.de/signup_user_complete/?id=xtdd8jyt6trbiezt71gaz3z4ge&md=link&sbr=su). Click the `GitLab` button, then `Sign in with Helmholtz ID`. You will be able to make an account by either finding your institution, or using your e.g. ORCID, GitHub, or Google account.
-
   * Connect to https://gitlab.iap.kit.edu, register yourself and join the "Air Shower Physics" group. Write to us on Mattermost (in the User Questions channel), or directly contact one of the [steering comittee members](https://gitlab.iap.kit.edu/AirShowerPhysics/corsika/-/wikis/Steering-Committee) in case there are problems with that.
   * Connect to corsika-devel@lists.kit.edu (self-register at
     https://www.lists.kit.edu/sympa/subscribe/corsika-devel) to get in

COLLABORATION_AGREEMENT.md → USING_COLLABORATING.md

-# Collaboration agreement
-
-The CORSIKA project very much welcomes all collaboration and
-contributions. The aim of the CORSIKA project is to create a
-scientific software framework as a fundamental tool for research. The
-collaboration agreement and the licensing model are based on the
-guidelines layed out by HSF
-[[1]](https://hepsoftwarefoundation.org/activities/licensing.html) or
-CERN
-[[2]](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwiLqKG00dXdAhUOZFAKHdIwAh4QFjAAegQIARAC&url=https%3A%2F%2Findico.cern.ch%2Fcategory%2F4251%2Fattachments%2F101%2F505%2FOSL-2012-01-Open_Source_Licences_at_CERN-Short_version.pdf&usg=AOvVaw1n4S0PQCSeE6wbdfdhKDqF),
-[[3]](http://legal.web.cern.ch/licensing/software), and follow the
-examples of other big scientific software projects.
-
-The CORSIKA project consists of the contributions from the scientific
+# Usage and collaboration agreement
+
+The CORSIKA 8 project very much welcomes all collaboration and
+contributions. The aim of the project is to create a
+scientific software framework as a fundamental tool for research.
+
+The project consists of the contributions from the scientific
 community and individuals in a best effort to deliver the best
 possible performance and physics output. 
-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. 
 
 
 ## The software license of the CORSIKA project
@@ -25,20 +15,24 @@ The license adopted for the CORSIKA project is the explicit copyleft
 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)
+source code release of CORSIKA contains the file LICENSE.
+
+The 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. 
+include, other licenses, which must be compatible with the CORSIKA 8 license. 
 
 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
+external physics models for your convenience. They each come with
+their own license which we ask you to honor.  Please also make sure to cite the
+adequate reference papers when using their models in scientific work
+and publications.
+
+Of course, we have the authors' 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.
+the build system to what extent this code is used to build CORSIKA.
 
 
 ## Contributing
@@ -46,4 +40,3 @@ the build system to what extend this code is used to build CORSIKA.
 If you want to contribute, you need to read
 [the GUIDELINES](CONTRIBUTING.md) and comply with these rules, or help to
 improve them. 
-

modules/fluka/README

+The FLUKA code comes with its own license that you can find at their project webpage:
+http://www.fluka.org/
+
+Please cite the following paper when using FLUKA in your scientific work and publications:
+F. Ballarini et al., The FLUKA code: Overview and new developments, EPJ Nuclear Sci. Technol. 10, 16 (2024)
+https://doi.org/10.1051/epjn/2024015 
+
+Should you use a container image of CORSIKA 8 with FLUKA already enclosed in binary form, please
+nevertheless go to http://www.fluka.org and create an account so that the authors can keep you
+updated on new developments.