"At the 'heart' of Linux operating system is its kernel - the code essential to the functioning of the system. While users add and modify different parts of Linux system, they are careful not to change the kernel in fundamental ways. Thus all dialects of Linux share the common core."
"From Models of Authorship in New Media" by Lev Manovich
full text at: http://switch.sjsu.edu/nextswitch/switch_engine/front/front.php?artc=65