[bergkvist]

I feel like looking at the first working versions of a big successful project is a great way to understand how it works.

Usually it will only contain the most important core features without a lot of abstractions/generalizations. So it is actually manageable to read through all of the code in a couple of days.

[SubjectToChange]

I don’t know about this. A lot of the success of a project has to do with how they react to changing conditions and the needs of their users. Moreover I would say that most projects owe a great deal of their success to the nontechnical factors, e.g. licensing or other social factors.

Reading the initial working versions of a successful project will inform you on how that project used to work. In a sense it’s akin to reading a working draft of a great piece of literature without reading the final product.