My final goal is to write the program which can run on the Unix OS. I know that there are many Unix versions, and don’t know exactly for now which one I need to support. I cannot install any Unix OS right now. The only thing I can do is to use free OS which is close to Unix as much as possible. Is FreeBSD a good choice for this? I know that there is also OpenBSD, possibly something else.
Additional information:
The programing language is C++, I am using GCC, with some portable libraries: Boost and wxWidgets.
OpenBSD, FreeBSD, DragonFlyBSD, NetBSD, Open Solaris, etc. are all open and free Unix operating systems, you cannot really get closer than that.
To circumvent the installation restriction consider virtualization with a tool like Sun’s Virtual box.