SourceForge.net provides a wide array of services, including developer web and project web. We encourage all users to back up their developer web data and project web data. Backups can be done with the file management service, accessible through web.sourceforge.net
Our file management service supports rsync, SFTP, SCP for downloads. FTP is not supported. rsync is the preferred method for retrieving backups since it allows the resume of partial transfers.
Examples for retrieving backups using each of these protocols are shown below. In these examples, replace U with the first letter of your SourceForge.net username, US with the first two letters of your username, USER with your entire username. Similarly, replace PROJECT with the whole UNIX group name of your project.
To synchronize your SourceForge.net home directory to a local copy:
rsync -avzPL -e ssh USER@web.sourceforge.net:/home/users/U/US/USER ./sf-net-backup-homedir
To synchronize your SourceForge.net project directory to a local copy:
rsync -avzPL -e ssh USER@web.sourceforge.net:/home/project-web/PROJECT ./sf-net-backup-projectdir
The first time you connect with rsync you will receive a warning about the authenticity of the host. And it will ask if you want to continue.

Follow the instructions on the Developer web and Project web pages for access using SFTP and substitute put with get. E.g.:
get htdocs/index.html
Documentation: Table of Contents - SourceForge.net Documentation