In my opinion, the gman isnt really a "man" at all, but rather an artificial construct created by some greater being, not seen by Gordon. Hes never (except by cheating or otherwise) physicly interacted with, and is completely invincible. Hes just a physical manifestation of some unseen force trying to maintane the space-time continuum.
The Black Mesa incident was both an opportunity to "recruit" people to use in the greater being's repairs of the space time continuum and to stop humans from accessing other dimensions.
The reason he kept Adrian is because of humans tendancy to die and the corporal's skills and abillity to adapt and survive through extreme circumstances. In other words, if Gordon dies, adrian comes in, but the GB thought that gordon would survive, which he has/will, both due to the game continuation, and due to the story line.
Aperature wasnt concerned because they were working on spacial teleportation, not interdimensional teleportation/transport.
The Black Mesa incident was both an opportunity to "recruit" people to use in the greater being's repairs of the space time continuum and to stop humans from accessing other dimensions.
The reason he kept Adrian is because of humans tendancy to die and the corporal's skills and abillity to adapt and survive through extreme circumstances. In other words, if Gordon dies, adrian comes in, but the GB thought that gordon would survive, which he has/will, both due to the game continuation, and due to the story line.
Aperature wasnt concerned because they were working on spacial teleportation, not interdimensional teleportation/transport.