Complex sentence: Carmack has on occasion commended the efforts of similarly focused programmers--first Ken Silverman, who wrote the Build engine for 3D Realms, and later with Tim Sweeney of Epic Games, who writes the Unreal Engine.
Split into simpler sentences: Carmack has on occasion commended the efforts of similarly focused programmers. First Ken Silverman, who wrote the Build engine for 3D Realms, and later with Tim Sweeney of Epic Games, who writes the Unreal Engine.