Lunar asked in the Halo.bungie.org forum (again) about what video cards, video APIs, etc Halo would use and got this response from Matt Soell:
Right now Halo uses OpenGL. D3D would pretty much cover the rest of the bases.I don't think we'll use any card-specific APIs. Obviously the degree of support we give to 3D cards is dependent on us GETTING cards to muck around with. (Thanks, nVidia!) Eventually we'll have one of everything and we should be able to add the various graphical frills everyone wants, or most of them anyway.
So it looks like no Glide in Halo. It also looks like we should rewrite Rampancy.net's forum software to preface the title of every post with Matt? :D