First of all, Unix (and even Linux) is NOT virus free. Although rare, there are viruses for such systems.
One of the primary reasons that Unix / Linux do not get as many viruses is that the ability of different users is limited. Non-technical users will be restricted in their ability to install, run, or modify software. More experienced users will usually be given more privileges. Without inexperienced users installing software at a whim, over 90 % of the threat of viruses and malware is removed.
Linux is even further protected against viruses because Linux is by nature a heterogeneous platform. To be effective, the program would have to be capable of affecting multiple versions of the kernel, and use exploits in a variety of programs.
Unix and Linux
If I understand your question....vague as it is....yes, the Unix OS source code is free and open source.
To create a Free OS like the UNIX Operating System, They wanted to create a system that was like UNIX without all of the intellectual property issues that UNIX had. (UNIX was proprietary software).
GNU is an operating system composed of free software. This operating system also has an icon which is a gnu,wildebeest head.GUJARAT NATIONAL UNIVERSITYGNU definition from gnu.org:The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software: the GNU operating system.after some research i came to know GNU acronym is "GNU's not Unix" here GNU stands for "Genuinely Not Unix" Operating System.
use linux operating system
Currently, The Open Group owns the "Unix" trademark. No, Unix branded operating systems are proprietary and copyrighted. They are not free or open systems software. From its start until 1993, Unix distributions included all their source code. Programmers have made many free and open Unix-like operating systems, including Linux, NetBSD, FreeBSD, OpenBSD, Dragonfly BSD, Mach, OpenSolaris, etc.
Linux or Unix are open source and some are versions are free and others aren't. Unix is based off of Linux, and both have many different variations. One popular Unix system is Ubuntu
Virus free is not true at all. However, virus writers have a harder time in a linux environment. and linux distros don't run as admin/root by default .
OpenBSD is a free an open-source Unix-like operating system, with a primary focus on security.
AntiVir or AVG are two good free anti-virus programs.
NetBSD is a free, open-source, unix like, multi-platform operating system descended from Berkeley Software Distribution (BSD) and based on 4.4BSD Lite.
No. Licensed Unix implementations are a proprietary flexible general purpose operating system originally marketed for minicomputers and mid-range computers to support multiple users and tasks. When Personal Computers became available, versions of Unix were created for them. Unix was also implemented for the IBM mainframe. This is not the same as Linux which is an open source free system with many of the same capabilities and look & feel of unix but without the licensing requirement of unix.