What are some alternatives?
When comparing NAS4Free and Zentyal, you can also consider the following products
OpenMediaVault - OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
ClearOS - A very good alternative for Windows Server, for free
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.
NethServer - NethServer is an operating system for Linux enthusiasts, designed for small offices and medium...
unRAID Server - A scalable, consumer-oriented, server operating system.