Thanks for explanations of the sub model seg fault.  Will correct that in next build.  And maybe other extended limit engines could use a check..
I've started trying to compile under Linux, trying to adapt TyrQuake sys_linux.c, etc., as a starting point.  This is the most current SW Quake Linux engine I could find.  Ran into a snag with X DGA libraries... lots of comments in headers stating "depreciated" and compile errors like "Pixmap undefined" within the DGA library headers themselves.  Anyone know what are the latest-and-greatest libraries to use?
Quake-based engine (Hexen II) including software engine (even transparent water and entities)  and lots of ports:  
http://uhexen2.sourceforge.net/  might be a source of knowledge.