It will share significant components with Servo/Gecko, and thus implemented in Rust.
We are more than happy to accept contributions to fix the rendering of any webpage you care about, and would consider it a bug if that's too complex of a task for you. At the same time we'll be kept busy with just the basics and trying new ideas out, so expect breakages.
The Memex was an early hypertext concept, which was going to be built using microfilm. Hypertext is what characterises The Web, and we wish to highlight that.