I have, in fact; but the only one where I did any serious work was on a closed source project that we licensed from the original devs who had shut down their service
to give you a taste of what it was like; there was a 2,000 line switch statement that basically translated inbound packet data (on the client-side) into Win32 window messages, internal state updates, sending packets back on the outbound queue, draw commands to DirectDraw, and x86 assembler that I still have no idea what it does
you can certainly build your own versions of the libs and supply 100 build flags, like --without-sqlite --without-postgresql --without-mysql --without-firefox --without-windows --without-office --without-nuclear-reactor-code --without-kitchen-sink --without-'fun'-bloat --without-holodeck ...
There was a lot that went into building our new blog - including the new engineering channel. See why it took us six to eight weeks to move to a new system, migrate our old content, and redesign the site.