The FreeBSD Foundation has announced that the name FreeBSD turns 25 years old on 2018-06-19. The mailing list archives contain a thread about name selection with with a message containing the following suggestion
How about just simply "FreeBSD"? No confusion, no fuss, seems like a good compromise to me. :-)
(Score: 1, Insightful) by Anonymous Coward on Wednesday June 20 2018, @03:41AM
Of course that is the license and not the operating system. Your patches can remain free and open. If you want to make a principled stand, you can license your patched version under the GPL.