BSD-0 is a public-domain-equivalent license. The guy who published it is one of the few people who has actually been involved in a lawsuit to try to assert a copyleft license. The whole thing was such a bad experience for him that he decided copyleft licenses are a false goal.

You should watch his talk:

https://www.youtube.com/watch?v=MkJkyMuBm3g

(He used to be a maintainer of busybox, a GNU clone for embedded devices. He then ended up writing toybox, a similar project under the more free MIT license.)