Always use pure vanilla kernel-sources from http://www.kernel.org/ to compile an openMosix kernel! Please be kind enough to download the kernel using a mirror near to you and always try and download patches to the latest kernel sources you do have instead of downloading the whole thing.
Be sure to use the right openMosix patch depending on the kernel-version. At the moment I write this, the latest 2.4 kernel is 2.4.22 so you should download the openMosix-2.4.22-3.bz patch, where the "3" stands for the patch revision (ie: the greater the revision number, the most recent it is).
Do not use the kernel that comes with any Linux-distribution: it won't work. These kernel sources get heavily patched by the distribution-makers so, applying the openMosix patch to such a kernel is going to fail for sure! Been there, done that: trust me ;-)
Download the actual version of the openMosix patch and move it in your kernel-source directory (e.g. /usr/src/linux-2.4.22). If your kernel-source directory is other than "/usr/src/linux-[version_number]" at least the creation of a symbolic link to "/usr/src/linux-[version_number]" is required.
Supposing you're the root user and you've downloaded the bzipped patch file in your home directory, apply the patch using the patch utility:
mv /root/openMosix-2.4.22-3.bz /usr/src/linux-2.4.22 cd /usr/src/linux-2.4.22 bzcat openMosix-2.4.23-3.bz | patch -Np1
... CONFIG_MOSIX=y # CONFIG_MOSIX_TOPOLOGY is not set CONFIG_MOSIX_UDB=y # CONFIG_MOSIX_DEBUG is not set # CONFIG_MOSIX_CHEAT_MIGSELF is not set CONFIG_MOSIX_WEEEEEEEEE=y CONFIG_MOSIX_DIAG=y CONFIG_MOSIX_SECUREPORTS=y CONFIG_MOSIX_DISCLOSURE=3 CONFIG_QKERNEL_EXT=y CONFIG_MOSIX_DFSA=y CONFIG_MOSIX_FS=y CONFIG_MOSIX_PIPE_EXCEPTIONS=y CONFIG_QOS_JID=y ...
Now compile it with:
make dep bzImage modules modules_install
Reboot and your first openMosix-cluster-node is up!