Those that have used the <license> elements in the <fileheader> section to date have put in something like this:</fileheader></license>
<license>
<licenseName>GPL (General Public License)</licenseName>
<licenseURL>http://www.gnu.org/licenses/gpl.html</licenseURL>
</license>
while the JSBSim Schema requires attributes:
<license licenseName="GPL (General Public License)"
licenseURL="http://www.gnu.org/licenses/gpl.html"/>
Someone's initial mis-interpretation that everyone else has followed, style from FlightGear or elsewhere, or does the schema need to be updated?
Note: Either way, it is a bit redundant to repeat the "license" on the element or attribute name, but that may be "too late" or can it still be changed (with a quick change to about 12 aircraft files in CVS.
OK, so it actually wasn't all of them, only 75% of them. And that was only 9 files. So I just fixed them...
I'll submit a patch in due time.