One of the Interix guys gave a talk at my local Unix group in 1997 or so.  He said they had a support contract with Microsoft. Once Windows NT came out, Microsoft stopped answering calls for about 6 months.  Because NT was going to win, right?<p>After 6 months, their technical contacts were sheepishly apologetic...<p>On a personal note, I did my main FreeRADIUS development on XP with Interix for many years.  It was... adequate as a Unix replacement.  Not spectacular, but adequate.<p>When that system died, I replaced it with an OSX system.  Which was enormously better.