Don't listen to the speculations. It's unhealthy.
H+ or h+ is the symbol for transhumanism (the idea of improving the human condition). The "3" simply stands for Deus Ex 3. The reason why H+ is bracketed is because H+^3 is something completely different and they want to (unsuccessfully, it seems) point out the transhuman context.
The Daedalus/Icarus dichotomy is actually based on literature (JBS Hanlane "Daedalus: Or, Science and the Future", in addition to greek mythology).