Switch to BSD Source Code Attribution license

[PandaScience]

Switch from BSD 3-Clause to BSD Source Code Attribution to prevent confusion around inclusion of copyright notices when distributing in binary form, i.e. compiled PDFs.

[PandaScience]

With regards to the recently started license discussion in #49 I'd like to ask all previous contributors to clearly state their consent or refusal to this change in license as a comment below.

The licenses in questions are [from] BSD 3-Clause [to] BSD Source Code Attribution, i.e. a migration to a more permissive license (see #49 for details).

Rejecting this change would regrettably force me to remove individual (genuine) contribution(s) for upcoming versions due to possible license incompatibility, except when they are trivial additions according to common sense, like fixing a typo, duplicating existing code just to add new icons etc.

🙏 @ifokkema @Bertbk @mikelyou @dverbeir @bigbenbeer @esben @DoctorD90 @Hespe 🙏

[Hespe]

No problems with the change from my side.

[esben]

You have my consent to the the proposed change of the license.

[ifokkema]

Of course, you have my consent, too! 🤗

[bigbenbeer]

No problem with the changes from me.

[dverbeir]

You have my consent too to migrate to BSD Source Code Attribution license.

[DoctorD90]

Objection, Your Honor! - Sorry, I've always wanted to say that. It's okay for me too!