Introduction to Software Licenses

Research Software Rights Management at Helmholtz, 26.09.2025, Online Tobias Schlauch <Tobias.Sc[email protected]> Institute for Software Technology German Aerospace Center (DLR) http://www.dlr.de/sc INTRODUCTION TO SOFTWARE LICENSES About me •Tobias Schlauch, M.Sc. in Computer Science •Works as software engineer at DLR and coordinates the DLR Software Engineering Initiative •Supports DLR researchers in context of the topics open source and software licensing in cooperation with the DLR technology transfer division Disclaimer: I am not a lawyer. The presented information result from my practical experiences and are no legal advice. If you need legal advice, please reach out to your legal team. Copyright basics •Copyright (German Copyright Act) •Copyright protects the expression of an idea and grants exclusive rights (“moral rights of authors”, “exploitation rights”) to the author •Software in its source and executed form including its accompanying material is also protected by copyright •Who is the author of a software? •All contributors are considered joint authors •All authors jointly exercise the rights granted by copyright and decide about the software license! Software license types Software Licenses Proprietary Free and Open Source Copyleft Permissive Public Domain Using code without a license or violating the license obligations can lead to a copyright violation! Free and Open Source Software Licenses •Open Source Software: •Characterized by the used software license •Idea developed in the early 1980s and originates from the Massachusetts Institute of Technology •Nowadays widespread adoption of open source software in research and industry •Free and Open Source Software Licenses: •Both terms can be use interchangeable and refer to the same set of licenses •Underlying definitions (Free Software, Open Source Definition) are maintained by the Free Software Foundation and the Open Source Initiative •Licenses imply the availability of the source code to the users and allow open distribution, modification, and code re-use OSI and Open Source Initiative are trademarks of Open Source Initiative: opensource.org. MIT license –Example of simple permissive Open Source Software License Copyright <YEAR> <COPYRIGHT HOLDER> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Copyright notice Granted rights Obligations Disclaimer Source: The MIT License –Open Source Initiative Copyleft effect •Copyleft effect: •Adaptations of an existing program must be placed under the open source license of the original program if distributed •Copyleft is determined by the technical usage and the concrete license •Strong vs. weak copyleft: •Strong copyleft licenses (e.g., GPL-3.0) require every modification and derivative works to be placed under the license of the original program •Weak copyleft licenses (e.g., LGPL-3.0) limit the copyleft effect, for example, to modifications of the library itself •Consequences: •Distribution of your own code under an open source license compatible with the copyleft license •Potential for license incompatibilities! Be aware of the consequences of copyleft licenses and consider licenses carefully when selecting libraries! License compatibility •License compatibility needs to be considered if you combine code under different licenses into one program! Overview about important Free and Open Source Licenses and their compatibility Source: David A. Wheeler, CC BY-SA-3.0, The Free-Libre / Open Source Software (FLOSS) License Slide License compatibility –Incompatible licenses example •License incompatibility exists when you combine code under different licenses with mutually exclusive license conditions! GPL-2.0-only LGPL-3.0-only Your Code Combination into one program not allowed due to license incompatibility! Reach out to legal support in “tricky” situations!