is there a blogpost about the process/what tools were used to do so?

This is _not_ a port of the (leaked) System 7 sources from 68k/PPC to x86. It rather seems to be reverse engineered from the 68k binaries.

From the project's README.md: "This is a reimplementation project for educational and preservation purposes."

See https://zenodo.org/records/17196870 for the related paper:

"we reconstructed a bootable prototype of Apple System 7.1 directly from 68k binaries in three days"

"We present an AI-assisted reverse engineering framework that achieves dramatic speedups—on the order of hundreds of times faster than traditional manual methods—by orchestrating specialized agents for evidence curation, struct recovery, and code drafting. Using this approach, we recreated a bootable prototype of Apple System 7.1 from binary analysis in just 3 days."