The NumWorks graphing calculator

Your understanding is correct.

He made an unofficial mod of the computer version of the NumWorks software, which features Giac integration; at the same time, he started putting some Python compatibility syntactic sugar into Giac. You can see a couple screenshots of NumWorks+Giac in the forum topic where I posted a link to :)
Apart from the HP Prime running an official mod of Giac, the TI-Nspire series has enjoyed his unofficial port of Giac since 2014, named Khicas (good pun, definitely intended), whose binaries are upgraded on a regular basis to follow Giac enhancements.