For the sample music and logo:

 ©All rights reserved by Project Moon. 
Other properties and any right, title, and interest thereof and therein (intellectual property rights included) not derived from 
Limbus Company belong to their respective owners. 
Please do not use or redistribute any part of this mod commercially. 
Find Project Moon's guide on the usage of their copyrighted materials at
https://steamcommunity.com/app/568220/discussions/0/2828702373002050715/

For the rest of the mod:
Free to use, modify and redistribute for non commercial purposes.