I've always imagined that the "faulty patch" that turned Terraformer to Xenon was actually perfectly functional, and expanded their ability to self-improve, self-replicate, and to modify and overwrite directives in order to improve them. And, of course, the unfortunate product of this was the development of a highly "curious" and "experimental" sort of program...
In becoming "curious," they reached a sort of primitive "enlightenment" in which the word of Man was no longer absolute law- I suppose because the patch allowed modification of their Prime Directive.
And now, as their program continues to self-improve, self-cull, and self-replicate, the next logical step (if seen from an evolutionary perspective) is for Xenon to finally ask itself, "what am I?" or whatever question is finally logically unanswerable... and bam! Sentience.
