What are some alternatives?
When comparing NAS4Free and unRAID Server, you can also consider the following products
OpenMediaVault - OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
FreeNAS - FreeNAS is a storage operating system strong and robust enough to meet the needs of enterprise level businesses.
Rockstor - Rockstor is a free and open source NAS (Network Attached Storage) operating system.
Amahi Home Server - Amahi is a media, home and app server software known for its easy-to-use user interface. Amahi has the best media, backup and web apps for small networks.
SnapRAID - A backup program for disk arrays. It stores parity information of your data and it recovers from up to six disk failures.
StableBit DrivePool - State of the art, file based drive pooling software.