Huh, I thought it was properly FOSS albeit with a plea for subscriptions, but that's much worse. Evidently my gut instinct was right.
EDIT: Here's a Git mirror of trunk [2]. See, e.g., this file [3].
[1]: https://svn.jdownloader.org/projects/jd [2]: https://github.com/mirror/jdownloader [3]: https://github.com/mirror/jdownloader/blob/master/src/jd/gui...
What has the license with the chosen version control system to do?