I have recently finished a work in which one of the chapters is based upon a translation of a nineteenth century document in which I have made use of a free online translator. Where the translator seemed to be at fault, I have done the translation myself; though in the end, the major portion of the whole translation used in that chapter relies on the output of the online translator.
The book, in three volumes, contains sixty chapters, only one of which, includes output from the the aforementioned translator.
QUESTION: Am I obligated to acknowledge the use of this free online tool; and if so, how should that be done? Can the writer of the software legally demand some sort of royalties when the book is published? I anticipate that it will be published in the United States.
UPDATE A follow-up to this question is found here: Copyright Ownership of a Translated Article Appearing in a Book in Which an Online Translator was Used