Bug 616193 made some changes to the about dialog, removing a string that mentions The Charlton Company (in favor of hardcoding it, only for en-US/GB). The relevant changeset is https://hg.mozilla.org/mozilla-central/rev/be63daa6e0f8 We just need to make sure that trademarkInfo.part1 in your locale refers to the Mozilla Foundation. trademarkInfo.part2 (the string that refers to The Charlton Company) is now unused and should be removed.
I checked that the current .part1 string does refer to Firefox and Mozilla, and not to the Charlton Company. (The .part2 string is gone.)
Good enough for me! Thanks.