In a world of growing importance of intellectual property rights it is unavoidable to think about copyright issues of a project as SymbolicData. We decided to consider the SymbolicData collection as a big “book” with common authorship (in the sense of, e.g., § 8 of the German UrhG) that should be freely available in digital form to all interested parties and that we are allowed to rearrange according to the decisions and latest technical achievements without further notice by the current and future project team.
Authors retain the copyright on their contributions but give an unrevocable nonexclusive right to use their contributions for the described purposes, i.e., the material can be modified, rearranged, produced derived work from it by the project team and any interested party. For benefit the contributors have free access - on the same rights as any community member - to the current version of the tools and data.
All these goals are best achieved with the regulations of the GNU General Public License (GNU GPL). This means that people all over the world can freely download and use the data under these terms and any derived work has to be given back to the community under the same terms.
Addendum: During the last years there is a strong discussion about the issue, that different free licenses, even GNU GPL, do not guarantee the right for cooperation in a way required for Linked Open Data. With PD (public domain) there are other legal problems - authors in different juridicial frameworks do not have enough rights to devote their work to Public Domain. The solution proposed is the usage of the CC-0 License. See also the CC-0 FAQ. This should be discussed within the Project Team.
But this also means that contributors have to accept those terms as inavoidable for a contribution. If you contribute to SymbolicData we silently assume that you accept to give an unrevocable nonexclusive right to use your contribution under the terms of the GNU GPL and that you are allowed to grant such rights. In particular this means, that you cannot publish the same contribution giving exclusive rights to a publisher. Nowadays, most of the publishers understand such a position.
Nevertheless, for sake of integrity of our data base we urgently ask you to refrain from contributing to SymbolicData if you are not willing or not able to meet these terms.