RendView is distributed for free under the GNU GPL.
If you use this program, you have to assist development by reporting any bug you find. And I mean that literally: You get the software for free and in return you report any bug you find.
Don't consider reporting bugs as something negative, dumb or stupid. It's neither negative for you (bug gets fixed) nor for me (as the programmer I want to provide a stable program).

You need a (more or less) POSIX-conformant operating system.
Windooze users: Sorry, you will have to get Linux (or FreeBSD, ...). [Hey, take a look at Knoppix.]
RendView compiles and runs natively under Linux as I (the developer) am using Linux for development.
Porting RendView to other POSIX-like operating systems should generally be easy but expect some fixes to be needed (tweaking with include headers, changing some system call). See porting below.

In order to compile RendView yourself (the recommended way), you need the following two packages: hlib and rendview. Always use the most recent tarballs available:

After downloading, unpack the files (tar xvfz or the like) and follow the instructions in rendview-0.7.1c/BUILD which tells you how to build HLib and then RendView. (Note that HLib now has its own pages with further information.)
You will need a C/C++ compiler, preferrably something above version 3.0 of the GNU compiler collection (GCC) as shipped with any recent Linux distribution. [Compiling gcc yourself from CVS sources isn't hard either...] Other compilers should theoretically work, too, with minor tweaking. The STL is not needed.
Furthermore, make sure you use GNU make (on some systems you have to use gmake instead of make).

Unfortunately, I do not have a complete computer farm at home (with one box for any major operating system), so I can only provide Linux binary packages for the ix86 platform.

If you get dynamic linker errors (shared object file not found) or get mysterious crashes or "illegal instruction" errors (SIGILL), please consider downloading the source package and compiling RendView for your computer.

Feel free to port RendView to any operating system you like. In case you did a successful port, please contact me so that the fixed incompabilities can be added to the standard source code and thus to future releases.
In case you do porting, expect to tweak around with some header files. This is done best by adding an appropriate check to configure.ac. Further pitfalls may be system call return values. I must admit that I may be a bit sloppy checking their return value. E.g. I may use
 if(close(fd))
 { Error("While closing %s: %s\n",path,strerror(errno)); ++fail; }
which will fail on some system which returns >0 in case of successful close and <0 in case of failure (SunOS?), so it should be:
 if(close(fd)<0)
 { Error("While closing %s: %s\n",path,strerror(errno)); ++fail; }
Be sure to do it carefully. I cannot add crude hacks to the source code but configure is our friend...

Unfortunately, RendView will have bugs.
For bug reporting instructions and a list of known bugs / missing features, see here.