So our resident expert on collecting rare synths and modernizing some has done it again. Datajake1999 has made an IBM Viavoice wrapper for sapi5. This, like the NVDA addon package, is legal as it does not contain any Voiavoice or Eloquence binaries. You will obtain them through purchasing a program that contains an Eloquence binary, the most legal method probably being Kurzweil1000 as that's the only currently available program that still contains a non-bound version of Eloquence.
For obvious reasons, this seems to only work under the 32bit sapi registry probably due to Eloquence itself not having a 64bit binary. But it is still definitely better than nothing, and better than dealing with the drm in Code Factory's build, as long as you have a legal means to access Eloquence.
https://github.com/datajake1999/SAPI5IBMTTS