Noone can legally make a game with this source code an sell it. Period. The license under which the code was released is explicit in this.
And HOTU is NOT generally legal. They strive to be, but, at the end of the day, they have not (to my knowledge) been granted permission to redistribute. They are technically in violation of some the EULA. It's one of those grey areas though, if someone cared enough to sue, then that means someone would care at some level, which means we could get direct answers to the distribution questions from some human being.
If folks want to make a game from scratch, standalone, license an engine. TGE makes a great starting place and is cheap and multiplatform. There are others, some free, some more expensive, some less. Making games is hard work. if you are going to work that hard, there should be the possibility of reward at the end of the endeavor.
Torque Game Engine and Torque Shader Engine are popular indie development tools:
http://www.garagegames.com I made a tech prototype of "Freespace Forever" back before hte source was released in a day based on that source. Kazan wanted to write an engine from scratch (hence ultimately, Ferrium).
Let me reiterate: There is no possibility of making a commercial game with SCP. None. Not until someone in authority changes the license under which this code was released.