Currently available for US English only.
What's considered profane? See this list (note: profanity ahead!) If you need to censor additional words not included in this list, use word replacements.
Sorry, but currently Web Captioner only works in Google Chrome.
You can still look around and play with settings, but in order to start captioning, you'll have to switch to Google Chrome.
If compatibility with browsers other than Chrome is important to you, cast a vote here.