[afruitpie]

The proprietary layout engine is named TALA. IMO the docs are pretty transparent about TALA being closed source and behind a paywall.

TALA docs: https://d2lang.com/tour/tala/

TALA product page: https://terrastruct.com/tala/

[weare138]

TALA is a separate install from D2, to keep a clean cut between 100% free and open-source D2, and proprietary, closed-source TALA.

It seems the 2 are distributed separately and D2 supports open-source layout engines also.