Just at the offset this does not constitute legal advice, just some opinions I have on this point. Technically, you would not be prohibited to generate speech and use it however you like. Under normal circumstances any output generated by the system that does not contravene the service agreement would be your intellectual property. This would include the text and speech generated. Once you go about the request limit you would naturally be required to pay, but until that time you can use the service as a paying customer.
Just to clarify this point I would like to make reference to the service license agreement, clause 3, which make reference to the following prohibitions:
(a) copy, modify, create a derivative work of, reverse engineer,
decompile, translate, disassemble, or otherwise attempt to extract any
or all of the source code of the Services (subject to Section 3.4
below and except to the extent such restriction is expressly
prohibited by applicable law); (b) use the Services for High Risk
Activities; (c) sublicense, resell, or distribute any or all of the
Services separate from any integrated Application; (d) create multiple
Applications, Accounts, or Projects to simulate or act as a single
Application, Account, or Project (respectively) or otherwise access
the Services in a manner intended to avoid incurring Fees or exceed
usage limits or quotas; (e) unless otherwise set forth in the Service
Specific Terms, use the Services to operate or enable any
telecommunications service or in connection with any Application that
allows Customer End Users to place calls or to receive calls from any
public switched telephone network; or (f) process or store any
Customer Data that is subject to the International Traffic in Arms
Regulations maintained by the Department of State. Unless otherwise
specified in writing by Google, Google does not intend uses of the
Services to create obligations under HIPAA, and makes no
representations that the Services satisfy HIPAA requirements. If
Customer is (or becomes) a Covered Entity or Business Associate, as
defined in HIPAA, Customer will not use the Services for any purpose
or in any manner involving Protected Health Information (as defined in
HIPAA) unless Customer has received prior written consent to such use
from Google.
Similarly, as specified here:
Customer will not, and will not allow third parties to: (i) use these
Services to create, train, or improve (directly or indirectly) a
similar or competing product or service or (ii) integrate these
Services with any applications for any embedded devices such as cars,
TVs, appliances, or speakers without Google's prior written
permission. These Services can only be integrated with applications
for the following personal computing devices: smartphones, tablets,
laptops, and desktops. In addition to any other available remedies,
Google may immediately suspend or terminate Customer's use of these
Services based on any suspected violation of these terms, and
violation of these terms is deemed violation of Google's Intellectual
Property Rights. Customer will provide Google with any assistance
Google requests to reasonably confirm compliance with these terms
(including interviews with Customer employees and inspection of
Customer source code, model training data, and engineering
documentation). These terms will survive termination or expiration of
the Agreement.
You should also take a look at this and this.
However, as per the terms of the agreement the speech generated would be your intellectual property, unless otherwise specified.
Good luck!
