I finally figured out what was going wrong. What it should have been is
this (and it's now in the ILE RPG source for the service program:
CREATE FUNCTION WTFOOBAR/CENSORACCT(NUMERIC(9,0)) RETURNS CHAR(1)
LANGUAGE RPGLE PARAMETER STYLE GENERAL NO SQL PROGRAM TYPE SUB EXTERNAL
(only the names were changed, to protect the innocent).
And I'll look into iNav, when I get a few minutes. But am I even
licensed on it?