According to the manual:

"For migrating a whole C-Script project over to lite-C, the best way is a step by step approach. Include an empty .c script at the end of your include list. The .c script may just contain the line #include <acknex.h> and empty .c #includes for every previously included .wdl file. Then move more and more declarations and functions from your C-Script code over to that .c script or to its includes, and make a test run after every block that you've moved over. Eventually you'll end up with empty .wdl files, and all code moved over to the .c files."

This implies that it's possible for C-Script code to include Lite-C code. Otherwise the step-by-step approach in the manual would be impossible. I also read a post from JCL indicating the same thing. He indicated it's not possible to run C-Script from a Lite-C program (because C-Script must be used only for declarations in a Lite-C program), but the reverse is possible.

Unfortunately, I haven't yet figured out exactly how to do what the manual and JCL seem to indicate is possible. If anyone knows how a Lite-C function can be referenced by a C-Script program, I'd love to know exactly how.