Absolutely, and those releases weren't even that old (<10 years). There are so many things that I learnt from tinkering with the Quake 3 source code in 2007, I

Absolutely, and those releases weren't even that old (<10 years). There are so many things that I learnt from tinkering with the Quake 3 source code in 2007, I am still very happy and grateful that I had the opportunity at the time. My understanding of topics like real-time applications, AI, platform independent code and debugging would be very different if that code would not have been released.