UDFs for the most part (at least in the ideal world) are not meant to be modified to make work in your environment. They are meant to work just like built-in KiX functions and should be treated as black boxes. That said, you should look over all UDFs carefully and try to understand what they do before implementing.

If you do modify a UDF, do not expect to get support from the author. If you must modify a UDF, it is important to disclose ALL modifications that were made if you are looking for support.
Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.