Douglas Wilder published one program though Atari Program
Exchange, Ultimate Renumber Utility, which he co-wrote with his
father, Justin Wilder. It first appeared in the winter 1981 APX
catalog, but was featured in the catalog for less than a year: in
the winter 1982 catalog, it was replaced by BASIC/XA, which did
renumbering as well as other functions for programmers.
This interview took place on January 26, 2018.
Teaser quote: "So we got enough money off the sales of that
through APX that it paid for both my father's computer and
mine."