License clarification

[hoijui]

Hello! :-)
most of the source files that are not copied from elsewhere, have no license info attached to them.
As it is now, I have to assume they are All rights reserved.

My bet would be, that you would want to use the jzy3d default license BSD-3-Clause, or the one used in the few files that do have a license header: AGPL-3.0-or-later.

If you can tell me, I would add a commit to the pull request I have open already: #2