test/optgroup.html was added on 2004-04-17 with no comment about licensing.
I contacted the author via <http://iccl.fi/feedback.cgi?id=mail>, asking
for a licence. The author noted that a developer of ELinks had originally
asked on the #debian.fi channel whether the file could be used, and he had
allowed it then. That permission grant had not been recorded in the source
tree though, and it is not clear whether modification had been allowed.
Anyway, the author now explicitly grants us the GNU free documentation
licence on this file, and is willing to consider other licences.
(cherry picked from commit fe78a0249a)
