Replying to gkronber:
We do not have to keep the old version in a branch. Do we have a policy how to branch/tag old versions of released plugins yet?
The old ALGLIB version is included in the tags of the released HeuristicLab versions. Therefore I think it is properly archived and we do not need to keep a branch for ALGLIB 2.5.0. However, if side-by-side installation of both ALGLIB versions is still necessary, the old ALGLIB version should also be kept in the trunk in order to include it in the next HeuristicLab release. But I think this is not necessary, right?