Supermemo

A reddit thread that goes over some ideas (use guidance from SM algorithms and create your own vs try to hook into a potential Supermemo API).

Creator of Supermemo and the related algorithms (such as SM-2).

Incremental Reading

Dendro
Supermemo

Subsequent versions of this algorithm are not open source, and used in Supermemo

This is not the same Incremental Reading as described in Supermemo, but it carries over a lot of the important aspects. The bigger aspect that is lost is the preservation of order and the ability to read a text both incrementally and sequentially.

Plenty of other readings from Piotr Wozniak, Andy Matuschak, Michael Nielsen, and others in the Supermemo, Anki, and other communities.