Folks, the add-on itself, IBMTTS which is the same as Eloquence, is perfectly legal and its link can be shared. The add-on is at ultrasound1372/NVDA-IBMTTS-Driver: This progect is to develop and maintain the NVDA IBMTTS driver. This repository is responsible for the x0_personal versions, which are continuing development even after it seems activity from the base repository has stopped.
However, what can't be shared because of legal issues, although many people have access to it, is the required library -- I mean ECI.dll and other *.dll and *.syn files. BTW the add-on (unlike the official release of Eloquence) makes use of extensive and advanced pronunciation dictionaries, and the project is hosted at thunderdrop/IBMTTSDictionaries
I can argue that the add-on is more responsive/crash-proof than the official Eloquence provided by Code Factory, and the addition of the community-driven dictionary makes it quite appealing.

Cheers,
Amir