Text to Speech usage help

I have a pronunciation game now use Google or Samsung TTS but their quality not high and receive many complaints from customer.

I have a plan to record voice from text to speech software available on website like:
IVONA Text-to-Speech Voices | TTS Voices | Text To Voice
https://www.acapela-box.com/

with no cost or pay them, simple i paste the word, record voice from PC sound card and use in my game.

But i don’t know if this violate their policy or not, i find on their website but can not see anything.

I know here someone have used acapela-box, please give me advice.

Update:

IVONA has excellent quality but it too expensive for use in commercial
acapela-box suit for me buy credit to download