add CC0-1.0 and replace licenses of djbdns

README.md

@@ -302,7 +302,7 @@ _Related: [DNS - Control Panels & Domain Management](#dns---control-panels--doma
 
 - [Bind](https://www.isc.org/bind/) - Versatile, classic, complete name server software. ([Source Code](https://gitlab.isc.org/isc-projects/bind9)) `MPL-2.0` `C`
 - [CoreDNS](https://coredns.io/) - Flexible DNS server. ([Source Code](https://github.com/coredns/coredns)) `Apache-2.0` `Go`
-- [djbdns](https://cr.yp.to/djbdns.html) - A collection of DNS applications, including tinydns. ([Source Code](https://salsa.debian.org/debian/djbdns)) `Public Domain` `C`
+- [djbdns](https://cr.yp.to/djbdns.html) - A collection of DNS applications, including tinydns. ([Source Code](https://salsa.debian.org/debian/djbdns)) `CC0-1.0` `C`
 - [dnsmasq](https://www.thekelleys.org.uk/dnsmasq/doc.html) - Provides network infrastructure for small networks: DNS, DHCP, router advertisement and network boot. ([Source Code](https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=tree)) `GPL-2.0` `C`
 - [Knot](https://www.knot-dns.cz/) - High performance authoritative-only DNS server. ([Source Code](https://gitlab.nic.cz/knot/knot-dns)) `GPL-3.0` `C`
 - [NSD](https://www.nlnetlabs.nl/projects/nsd/about/) - Authoritative DNS name server developed speed, reliability, stability and security. ([Source Code](https://github.com/NLnetLabs/nsd)) `BSD-3-Clause` `C`
@@ -724,6 +724,7 @@ VPN software.
 - `BSD-2-Clause` - [BSD 2-clause "Simplified"](https://spdx.org/licenses/BSD-2-Clause.html)
 - `BSD-3-Clause` - [BSD 3-Clause "New" or "Revised"](https://spdx.org/licenses/BSD-3-Clause.html)
 - `BUSL-1.1` - [Business Source License 1.1](https://spdx.org/licenses/BUSL-1.1.html)
+- `CC0-1.0` - [Public Domain/Creative Common Zero 1.0](https://spdx.org/licenses/CC0-1.0.html)
 - `CDDL-1.0` - [Common Development and Distribution License 1.0](https://spdx.org/licenses/CDDL-1.0.html)
 - `EPL-1.0` - [Eclipse Public License 1.0](https://spdx.org/licenses/EPL-1.0.html)
 - `GFDL-1.2` - [GNU Free Documentation License 1.2](https://spdx.org/licenses/GFDL-1.2.html)