Hi,
No, they all write their own these days. None available to license as far as I'm aware.
Most times the "proprietary" NAS software is simply a web interface over a standard Linux/FreeBSD OS using Samba. If you know Samba and Linux, the web interface may be a hurdle, not allowing access to features you know how to configure from the shell or, worse yet, overwriting those settings, if they provide a shell at all.
[]s, Fernando Lozano