Adopt LGLP-v2

[JeromeCCP9]

[] change license file
[] change file headers
[] change website, docs to reflect change

[LecrisUT]

If this one gets in, that's another place to update the license. Granted I have not done a license review to see if the GPL-2.0-only is actually correct and if there are not any differently licensed files that were not accounted for.

[JeromeCCP9]

fixed in #618 and #598