My last name makes me invisible to Computers (2015)
I've been programming for over a quarter century, and I feel pretty confident that I've never written anything that could confuse 'null' with NULL.   I can't even think of a language that would let you easily do this.If web forms aren't accepting NULL, then somebody probably specifically programmed the word 'null' into a filter of disallowed entries.  Probably to stop clerks from entering the word 'null' to mean empty string.  This has nothing to do with null being a reserved word in many languages, I'll bet the forms that aren't accepting 'null' aren't accepting 'none' or 'empty' either.