A Unix-like (sometimes shortened to UN*X or *nix to circumvent trademark issues) operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification.
There is no standard for defining the term, and some difference of opinion is possible as to the degree to which a given OS is "Unix-like".
The term can include free and open source operating systems inspired by Bell Labs’ Unix or designed to emulate its features, commercial and proprietary work-alikes, and even versions based on the licensed UNIX source code (which may be sufficiently "Unix-like" to pass certification and bear the "UNIX" trademark).
Free and open source examples are sometimes known as Freenix.
The term "Unix-like" and the UNIX trademark
The Open Group owns the UNIX trademark and administers the Single UNIX Specification, with the "UNIX" name being used as a certification mark. They do not approve of the construction "Unix-like", and consider it a misuse of their trademark. Their guidelines require "UNIX" to be presented in uppercase or otherwise distinguished from the surrounding text, strongly encourage using it as a branding adjective for a generic word such as "system", and discourage its use in hyphenated phrases.
Other parties frequently treat "Unix" as a genericized trademark. Some add a wildcard character to the name to make a euphemistic abbreviation like "Un*x" or "*nix", since Unix-like systems often have Unix-like names such as AIX, HP-UX, IRIX, Linux, Minix, Ultrix, and Xenix. These patterns do not literally match many system names, but are still generally recognized to refer to any UNIX descendant or work-alike system, even those with completely dissimilar names such as Solaris, FreeBSD or Mac OS X.
As of 2007, there is an active legal battle between Wayne R. Gray and Open Group that centers on the use of UNIX as a trademark. Trademark Trial and Appeal Board court documents indicate that Gray’s legal team is seeking for the Open Group to provide documentation for their trademark claim.
Full article ▸