Yes I know Asterisk is ridden with bugs and has very nasty spots at its core (e.g. "channel cloning" or whatever it is called). It was my job to debug the code

Yes I know Asterisk is ridden with bugs and has very nasty spots at its core (e.g. "channel cloning" or whatever it is called). It was my job to debug the code with gdb and valgrind :) What is still amazing to me is the set of core design concepts which I've listed - channels, applications... I have a case for comparison here, where the project is of comparable complexity but all features are bolted-on ad-hoc without such complexity compartmentalization which Asterisk has.