KindFTP is meant to be a complete implementation of the FTP protocol, as specified in RFC959. It provides a component that directly exposes the low-level protocol, and it supports the core protocol that is available on most Open Source FTP servers. It has untested support for ACCT, SMNT, REIN, TYPE, STRU, MODE, ALLO, and SITE command. It uses iContract to provide a full formal specification of all software, jUnit for all unit testing, and Ant as a build tool.
DrFTPD is an FTP server written in Java. It does not handle transfers in the same way that normal FTP servers do. Instead, it merges multiple FTP sites into one, creating a distributed FTP site/FTP cluster containing one master and many slaves/nodes. When a client wants to transfer a file from DrFTPD, DrFTPD finds the slave which has the file, and tells the appropriate slave to transfer the file instead of handling it itself. This allows huge gains in total bandwidth and disk capacity.
Oliver (formerly "WebShare") is a PHP-based FTP front-end, released under the GPL. It allows people to access files normally only available via FTP, effectively providing users with a complete Web-based file management system that, if SSL is enabled on the Web server, uses a single secure connection. This makes it far simpler to use through a firewall. At present, Oliver has only been tested with ProFTPd and PureFTPd but it should work with many others.
NASLite is a Network Attached Storage (NAS) server operating system designed to transform a basic computer into a dedicated file server. Utilizing highly optimized versions of Samba, uCLibc, BusyBox, and various other Linux tools, it provides SMB/CIFS, FTP, or NFS filesystem support. It accommodates multiple client OSes: Windows, Mac OS X, and Linux. NASLite offers SMART disk monitoring and large file support, and is incredibly easy to install and administer.
AnomicFTPD is an RFC959-compliant FTP server with OS- independent user and group management. Active and passive modes, non-root mode, and anonymous and/or read-only modes are supported. A built-in client IP filter acts as a firewall and provides additional access limitation. The server has no online interface; attributes, groups, and user accounts are configured through text files. The protocol/ format-unspecified LIST command produces output that is compatible with most FTP clients, including common Web browsers in FTP mode.