Most open source licenses have an attribution and license-preservation clause specifically so buyers know that the software contains things derived from OSS cod

Most open source licenses have an attribution and license-preservation clause specifically so buyers know that the software contains things derived from OSS code. I can certainly sell you ReallyCoolSSL which is just a rebranding of OpenSSL, but you're going to see the OpenSSL license and then go wonder what OpenSSL is. Works in the public domain do not have a license and therefore do not have this obligation to tell people what's going on.