FileZilla is a free FTP solution with FTP client and FTP server programs developed by Kim Kosse. FileZilla supports FTP, FTPS and SFTP protocols and multiple platforms: Windows, Linux, Mac OS X and more. FileZilla is open source software distributed under the terms of the GNU General Public License.
Filezilla is a pair of programs, an FTP server and an FTP client. They are used for transferring files over a network. The software is legal. Transferring files may or may not be depending on if they are protected by copyright or not and (if they are) if the owner of the copyright has granted permission.