You can use it as you want.
Answer from Juanjo Valdivia on learn.microsoft.comVideos
On Windows about the best I have found was using the speech API and voices from AT&T Natural Voices: https://nextup.com/attnv.html They are however VERY expensive if available at all. I have run into projects where the usage/business model was so far from what AT&T was thinking of that they wouldn't even sell a license.
There is a free software alternative, Festival: http://festvox.org/ , the quality though is horrible. It is about 10 years behind the current sound quality of commercial systems. It is however free.
A third alternative which has worked well for me was to shift the voice synthesis part of a few projects to OS X. OS X has a decent set of tools and speech APIS and a fairly decent set of stock voices. The downside of course is that prorams written for these APIs run only under OS X which runs only on Apple hardware.
AT&T Natural Voices engine produces great speech but its not free
there is also NeoSpeech which are also good - Not free as well