All relevant authors have agreed to the relicensing.
Problem cases:
eca47b1a5e: someone else gets credited for the "idea" of this change,
but it doesn't seem like it was a patch (otherwise reimar would have
said "patch"). Also, the associated code got essentially removed again
anyway. (The option parsing was rewritten fully.)
ffb529e4eb: anonymous/unknown author, but the code was fully removed
anyway. The struct was removed, and the modern code does explicit
read/write calls.
40789473d2: author was not contacted, but this code was removed
anyway. The magic number (0x7ffff000) is still in the new code, but I
don't think that is copyright relevant.
c750b8ab2d: the message was entirely removed.
43aaba4f73