Wish there was some context to this, and/or any info as to where the code is from. Is it an implementation from scratch of a specific (and interesting) subset?

Wish there was some context to this, and/or any info as to where the code is from. Is it an implementation from scratch of a specific (and interesting) subset? What's the angle? Low resource? Low code complexity? One specific feature subset? Not blaming the repository authors! Github is also a dumping place. More interested by what zdw thought of it when posting the link and whether anyone has any more info here?