Comment by londons_explore

Worth noting that while AlphaGo and AlphaZero are incredible achievements, the amount of actual code to implement them isn't very much.

If you have the research paper, someone in the field could reimplement them in a few days.

Then there is the large compute cost for training them to produce the trained weights.

So, opensourcing these bits of work without the weights isn't as major a thing as you might imagine.