In the small-ish world of open-source & embedded graphics, toolkits, and SW / HW rendering implementors, there are few who have been at it as long and have such a breadth / depth of experience in so many areas as yourself.
As someone who has done a fair bit of searching for resources on the theory and practical design of such systems, I must say, that there are few books out there that concisely describe the "how" and "why" in a design-patterns kind of way tie in with immediately relevant topics (e.g. fbdev, widget & drawing libs, scene-graphs). Naturally, implementors often pick up the talent and ensure that trade secret is kept that way, but you are at a bit of an advantage I think, no?
You've been at E for a *long* time and you've done an insane amount of work making SW rendering almost as efficient as HW rendering - I'm sure there is no shortage of material.
Have you ever thought about writing a book - sharing some of your expertise with the world in a less formal language? Not something that's all-encompassing by any means but maybe with references for further reading. What about a techno-biography of E?