Here is the difference between Linux and unix.
Many a times we get confused with Unix and Linux also threat them as synonyms but that is not true. UNIX is copyrighted name only few of the companies are allowed it i.e. IBM AIX and Sun Solaris and HP-UX. This quote from Official Linux kernel README file confuses most:
Linux is a Unix clone written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX compliance.
In this article I am trying to describe the various differences between Unix and Linux under the following headings -
1. History
2. Usage
3. Cost
4. GUI
5. Security
6. Future OS
History
UNIX was created in the 1960s by the AT&T Bell Labs (Ken Thompson and Dennis Ritchie) and first commercially UNIX OS became available in 1970. First release of Unix was having a command line interpreter and some small utility programs with future extension for the multitasking and UNIX evolved from there.
In 1991, Linus Torvalds began working on a UNIX like OS known as Minix. The Minix source code was freely available under GNU GPL and he successfully modified this code for use on x86 PC systems. By September 1991, Torvalds has successfully completed the first Linux kernel designed for PCs. This kernel included various system utilities and libraries from the GNU project to create a usable operating system based completely on open source code.
Usage
The UNIX operating system is used in internet servers, workstations & PCs. Backbone of the majority of finance infastructure and many 24x365 high availability solutions.
Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers.
Cost
Linux is Free (as it is opensource, except the case where you need a supported version i.e. RHEL). You can download it from the Internet or redistribute it under GNU licenses. You will see the best community support for Linux. Most UNIX like operating systems are not free (but this is changing fast, for example OpenSolaris UNIX). However, some Linux distributions such as Redhat / Novell provides additional Linux support, consultancy, bug fixing, and training for additional fees.
GUI
Any modern system discussion can not be completed untill unless we discuss about graphical interface. Linux typically provides KDE and Gnome, but there are many alternatives such as LXDE, Xfce, Unity, Mate, twm, ect. where as Unix most distributions now ship with Gnome (initial GUI used to be called CDE i.e. Common Desktop Environment)
Security
Linux comes with open source netfilter/iptables based firewall tool to protect your server and desktop from the crackers and hackers. UNIX operating systems comes with its own firewall product (for example Solaris UNIX comes with ipfilter based firewall) or you need to purchase a 3rd party software such as Checkpoint UNIX firewall.
Future OS
Linux is the fastest moving operating system if we exclude the Android (android can be thought of evolution from UBuntu) whereas Unix is slowly becoming obsolete.
Reference:-
http://tech.queryhome.com/47860/comparison-between-linux-and-unix-operating-system