All LegacyClonk content (graphics, sounds, scripts, etc.) is licensed under CC-BY-NC.
The only exception is engine code, which is licensed under ISC.
Thus, everyone who contributes content (as defined above) to LegacyClonk needs to state their commitment clearly with a post in this thread.
The post should contain something similar to:
I hereby license all my current and future contributions to LegacyClonk under the CC-BY-NC license.
Whoever commits the content into the LC repository will mention your contributions in the according COPYING file in the repository.