What are some alternatives?
When comparing BulletProof FTP Server and SFTPPlus, you can also consider the following products
FileZilla Server - Download FileZilla Server 0.9.60.2 for Windows
ProFTPD - The Official ProFTPD web site. ProFTPD is a high-performance, extremely configurable, and most of all a secure FTP server, featuring Apache-like configuration and blazing performance.
vsftpd - Very secure FTP Daemon, a secure, fast FTP server for UNIX systems, including Linux.
Baby FTP Server - The simplest FTP server to setup. No authentication required.
mosh - Mosh (mobile shell), the mobile SSH replacement.
Serv-U FTP Server - FTP server software