To answer questions so far (I'm the author of learnbhcs): yes, folks use BSD to host servers (if you want HTTP/2, there's nginx, etc.); kcgi interfaces with either CGI or FastCGI depending upon what the caller wants; yes, folks use this.
No. openrsync implements the rsync protocol. It doesn't have all of its options, but the protocol is what it is. Do you have any idea what you're talking about?