I'm not sure which of the following two questions you meant to ask (though I guess probably the second one), so I'll answer both:

(a) "Under what circumstances is something (either an l-zombie or conscious)?" I am not saying that something is an l-zombie only if someone has actually written out the code of the program; for the purposes of this post, I assume that all natural numbers exist as platonical objects, and therefore all observers in programs that someone could in principle write and run exist at least as l-zombies.

(b) "When is a program an l-zombie, and when is it conscious?" The naive view would be that the program has to be actually run in the physical world; if you've written a program and then deleted the source without running it, it wouldn't be conscious. But as to what exactly the rule is that you can use to look at say a cellular automaton (as a model of physical reality) and ask whether the conscious experience inside a given Turing machine is "instantiated inside" that automaton, I don't have one to propose. I do think that's a weak point of the l-zombies view, and one reason that I'd assign measureless Tegmark IV higher a priori probability.