First of all, you must understand that openMosix is made up of a kernel patch and some user-space tools. The kernel patch is needed to make the kernel capable of talking to other openMosix-enabled machines on the network. If you download openMosix as a binary package (such as an rpm file), you don't even need to take care about the kernel patch because the kernel has been patched and compiled with the most common default options and modules for you.
The user-space tools are needed in order to make an effective use of an openMosix-enabled kernel. They are needed to start/stop the migration daemon, the openMosix File System, to migrate jobs to certain nodes and other tasks which are usually accomplished with the help our good old friend: the command line interface. About binary packages: the same as in the kernel patch goes for the user-space tools: if you install an rpm you don't need to care about compiling them or configuring anything; just let them install and run. That's all. Really :)
Once you get to the download page (which we'll talk about in a second), you'll need to get two distinct parts: the kernel and the user-space tools. You can either download two binary packages or get the kernel patch plus the user-space tools' sources. The kernel patch is usually named after this scheme: openMosix-x.y.z-w where x.y.z is the version of the vanilla Linux Kernel against which the patch should be applied and w is the patch revision for that particular kernel release. For the precompiled kernel binaries, please refer to the README-openMosix-kernel.txt file you'll find in the download page. This file also contains updated info about manually compiling a kernel.
About the user-space tools: you'll find those in a package named openmosix-tools. We use the terms user-space tools, userspace-tools and openmosix-tools interchangeably. Updated info about precompiled binaries and manually compiling the tools are also provided in the README-openmosix-tools.txt file. Please note that since version 0.3 of the openmosix-tools, the openmosix.map file is deprecated and the use of the autodiscovery daemon is highly encouraged since it tends to make your life easier.