The Constitution isn't copyrighted, "One nation under God" isn't in the Constitution and wasn't originally in the pledge, the line is "with liberty and justice for all" and I don't believe "and justice for those who threaten liberty" was ever part of anything.
In short this guy is impressively wrong.
Kinda curious as to who he thinks threatens the liberty of Americans, but I'm sure I can guess with disturbing accuracy.
Off Topic: My post count is 300. 301 isn't a good number, so I feel like I can't post again.