Haven't gotten a chance to check this out in detail, but this project to produce a new font renderer using the Rust programming language looks very interesting: https://medium.com/@raphlinus/inside-the-fastest-font-renderer-in-the-world-75ae5270c445
Beyond the large speed-up claimed by the initial post, using Rust has some interesting implications in how inherently stable programs written in it are. There have been a growing number of C-to-Rust rewrites, and it would be great to see some of that effort come to the underlying font software as well.
Sidebar: this isn't exactly "Type Design Software", but that seems to be the closes category available. Mods, perhaps just "Type Software" would be sufficient and more usefully general?