What about "Id Software"? I think it's pronounced id as in:
"id - the one of the three divisions of the psyche in psychoanalytic theory that is completely unconscious and is the source of psychic energy derived from instinctual needs and drives"
- Merriam Webster.
But I always say ID (Identification), I think it sounds better.
Also there is GUI, I say the letters, but some people say "gooey".