For those unfamiliar with EGL, it's an API that's maintained by the Khronos Group and serves as a binding API to OpenGL, OpenGL ES, and other rendering APIs. EGL is described by the Khronos Group as:
EGL is an interface between Khronos rendering APIs such as OpenGL ES or OpenVG and the underlying native platform window system. It handles graphics context management, surface/buffer binding, and rendering synchronization and enables high-performance, accelerated, mixed-mode 2D and 3D rendering using other Khronos APIs.
During Kristian's XDS talk he talked about using EGL with sharing resources across different APIs (using the EGL image extension), his work to run EGL on the KMS frame-buffer directly, a Khronos API for sharing EGL images between processes that is similar to the extension created for DRM/Mesa, and the state of the EGL API within Mesa and Gallium3D.
It was after adding the EGL_MESA_DRM_image extension to Mesa that it became possible to run Wayland off mainline Mesa. Wayland uses EGL and previously this support was provided by a side-project of Kristian's known as Eagle before it was merged into Mesa.
Below is Kristian's XDS 2010 EGL talk in two parts.