"make" and "make install" should do the trick.

iowarrior.c gets compiled to iowarrior.ko.
An already loaded iowarrior module gets unloaded.
iowarrior.ko gets copied to /lib/modules/<your kernel version>/kernel/drivers/usb/misc
where it belongs.
The module is then added to the module dependencies and gets loaded.

Additionally make_nodes is executed which creates the device nodes
/dev/usb/iowarrior0 to /dev/usb/iowarrior15.
Each node pair represents a single IO-Warrior. Even numbers give access
to the I/O pin pipe whereas odd numbers give access to the Special Mode pipe.