A while back I had to provide web access to an FTP server and found something called Web-Ftp It is written in Perl. Idont know if this would be a drop in solution for you but it could give something to work off. It is a GPL/Artistic Licenence.

Disclaimer: It has been a while since I have used this. Also i used it for only in-house people and didnt go over the security of the script so use with caution