The module-init-tools are a set of programs for loading, inserting, and removing Kernel Modules for Linux (versions 2.5.48 and above). It serves the same function that the modutils package serves for Linux 2.4. They are necessary because starting with 2.5.51, modules are handled differently. Every symbol of a module has versioning information, so that the Kernel can read the module and what hooks it uses, compare it to an internal database of what's critical and what's not, and decide whether the module can be used, even if it wasn't compiled specifically for the current running Kernel. This adds a lot more flexibility for people forced to run BinaryDrivers.
You might have ModuleInitTools already installed without knowing it. The ModuleInitTools can coexist with modutils on the same machine. The old modutils binaries will have .old (or .modutils for DebianLinux users) appended to their names, and will be called by the ModuleInitTools equivalents if a 2.4 series Kernel is detected. Most modern distributions are already set up this way. If this is the case then the make moveold target of the ModuleInitTools MakeFile will destroy your setup! The make install target is harmless, you can use it to upgrade your ModuleInitTools without affecting the old modutils.