DeleGate is a multi-purpose application level gateway or proxy server that mediates communication of various protocols, applying cache and conversion for mediated data, controlling access from clients, and routing toward servers. It translates protocols between clients and servers, converting between IPv4 and IPv6, applying SSL (TLS) to arbitrary protocols, merging several servers into a single server view with aliasing and filtering. It can be used as a simple origin server for some protocols (HTTP, FTP, and NNTP).
linux-ftdp-ssl is the netkit ftp server with encryption support. ftpd-ssl replaces normal ftpd using SSL authentication and encryption. It operates together with normal ftp. It checks if the other side is also talking SSL, if not it falls back to normal ftp protocol. Advantages over normal ftp(d) are that your passwords and the data you send will not go in cleartext over the line, and nobody can get it with tcpdump or similar tools.
ftp-ssl is similar to the standard FTP client and it interoperates with normal ftpd, but it uses SSL authentication and encryption. It checks if the other side is also talking SSL, and if not it falls back to the normal FTP protocol. Advantages over normal FTP include encryption of passwords and transmitted data, preventing network sniffers from acquiring secret information (most notably passwords).