While the code of the cl_default mod was written from scratch it often follows the
original C++ code closely, so out of caution LGPLv2.1 (or later) was chosen as license.
Most media files were directly copied from Minetest-c55 0.3.1 which is CC BY-SA 3.0.
For details please check the LICENSE.txt files in individual mods, notably cl_default.