With the X11 Server having been around much longer than Wayland (Wayland is only four years old where as X11 is 25 years old albeit the modern X11/X.Org Server just has nearly a decade and a half of history in its Git repository), the visualizations produced by Gource are much more interesting for X11. There's been hundreds of contributors to the X11/X.Org Server during this time and major code re-factoring.
Here's what the X11 Server development looks like since 1999 while compressed into three minutes of history:
For development statistics, the top contributors to X11 and their corporate affiliations, etc are outlined in this article.
The Mesa OpenGL development going back to 1999 is also an interesting display:
Here's some stats about the Mesa development history for those interested.