I have a definite answer. While NIS+ is no longer supported, it is still owned by Sun Microsystems and is not open source. My source is : Siever, E (2005) Linux in a Nutshell. 5th ed. California: O’Reilly & Associates, Inc., pp 29.

Thanks for the info GE9. I've sent away for a book that may help. I'll post my findings when it turns up.

Hello everybody. Does anybody know if NIS+ is open source or is it proprietary? (I know a lot of people recommend avoiding it but I need to find this out). If anybody could suggest a website that would provide a definitive answer I would be very grateful.