There is nothing to stop you adding your own stuff to USNI. Thomas did the it with SCX. You'll see new entries for all the new units that SCX brought along.
I think MaHuJa is right as the data in the USNI is from the USNI so in effect they have paid USNI for the right to reproduce the material.
But add your own errata or notes. Easy to do and I think would be helpful.
Call it Luft/Ami Mod notes.
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