"INCLUDE" == "CALL" for non-tokenised scripts.

For tokenised scripts INCLUDE will merge in the named file as in-line code during the tokenisation process.

I would have thought that the merge of UDFs is better done by an additional step when you create your package or "release" the script to your live environment.

Having the merge done by an additional step makes the process more manageable. When you update your library, just run "mergeudf *.kix" to update all your scripts with the new library.