You automatically have a free trial and you don't have to create an account to use BenkoBot. You control access with your Trello API Key and a token that allows BenkoBot to interact with Trello on your behalf.
Just make sure you're logged into Trello and then head over to the login page to get your key and generate the token.
* You can set up and host Trellinator yourself but BenkoBot makes the whole thing more powerful and much (much, much much) simpler. These gists and the Atlassian forums are a good place to get an idea of what you can do with Trellinator.