Dan Bernstein took that attitude back in the 90s - I think his personal theory of copyright went something like "if it doesn't have a license, then it's obviously public domain", which ran counter to the mainstream position of "if it doesn't have a license, then you have to treat it as proprietary".
And, sure, djb wasn't actually likely to sue you if you went ahead and distributed modified versions of his software... but no-one else was willing to take that risk, and it ended up killing qmail, djbdns, etc stone dead. His work ended up going to waste as a result.