Kernel Module from C program

Greetings, I'm new to the world of kernel modules programming. I've read the Linux Kernel Module Programming Guide by Peter Jay Salzman, among other documents, and I have the following question: I'd like to know if it's possible to take a program developed in C (in this case OpenSIPs, which is a SIP Proxy Server) and turn it into a kernel module (I know "to turn it" is probably not the right expression, what I mean is if I could modify it somehow so that it can be loaded as a kernel module) ? As far as I've understand, kernel modules are developed for drivers or to do some modifications to system calls, but I like to know if it's possible to do what I stated earlier. Thanks, Luis Morales.