I'd like to ask about libraw (and libraw-lite) licensing.

Both libraries share the (almost) same code, and both are licenced under LGL 2.1; but libraw can be distributed choosing one of three available.

What are the main reason for this?

Reading the source, I can notice some comments like 'LIBRAW_DEMOSAIC_PACK_GPL3' or 'LIBRAW_DEMOSAIC_PACK_GPL2'... what is meaning? Portion of the code can be included only if distributed which some licences?

Thanks for your time!