All authors of the current code have agreed.
For most of its life, MPlayer used Microsoft structs like WAVEFORMATEX
to describe media content. It appears these were copied from wine in
61c5a99851. Copyright is unclear, but mpv completely removed use of
these structs anyway. (demux_mkv.c still contains code to read these
fields from a byte stream, but the struct is fully gone.)
42f97b2b820: cehoyos (who probably didn't agree with LGPL) applied a
patch by someone who agreed. It's unknown whether cehoyos modified the
patch (and thus his copyright would apply), but the changed code was
removed anyway. (The code was first moved somewhere else, then removed.)
efd53eed614: the patch author was not asked. Although the mkv_sh_sub_t
struct was later moved to stheader.h, the added field was removed
without replacement.
f6878753fbd: nick, who could not be reached, added an include guard, but
the guard was changed several times later, and it's probably not
copyrightable anyway.
afb0fd5ea17: the same nick adds a field that was later replaced and
finally removed again in 8cd6b20571.
6aba929a1b