It's quite easy to use (creates and auto file automatically) and has already been used in commercial projects.

@WHE, I'm no attorney, but I know of no legal issue as long as you are using original text to generate your audio files. I'd suggest you be very careful if you are using text that your organization did not write or that you don't otherwise know with absolute certainty is free from any copyright issues. The tool is intended for both commercial and non-commercial work.

I have uploaded several videos to YouTube with voiceover created using Vegas TTS and I got no issues at all. All the text was my own creation. This feature is amazing.