GOG should enable these missions in the game by default. They don't add much, but the audio logs are such an integral part of the main story that it should have been downright criminal to restrict this content from ordinary copies of the game.

Fuck gamestop.

I cannot get ANY of the promo codes to work on the GOG version.

They worked OK for me. See: http://www.gog.com/forum/far_cry_series/far_cry_2_unlocking_more_extra_content