Hi Fritz,
It looks as if you can add CSS to the class .g-recaptcha. setting the right and left margins to auto should center the content.
Bob
CF uses semantic UI, have a look at its documentation for styling help.
I understand (I can guess) what you're talking about, but my comment is directed to a usage for the CF component more (standard-)user friendly. I can create websites using a cms that are already written/programming (like joomla) and I are of years a regular user of the Rockettheme templates (with rwd Gantry5). Although I know the user interfaces of these platforms, managing to customize a custom style sheet, while creating logos and drawings with vectorial and bitmap graphics platforms, I consider myself a simple standard user and not a php code programmer.
Every time I read answers like yours, I ask myself how many standard users like me, have the time and are able to pick up (and learning) guides and programming summaries to solve small issues. ...and I do not even want to go into the field of linguistic knowledge, which too often uses common use technical abbreviations.
I apologize for my previous post, that didn't want to be a criticism but a simple suggestion.
You don't need to be a programmer to use semantic UI it's the whole point of it. If you had a look you would understand that. Instead of flooding the forums with simple questions you could try to research what I took the time to try and tell you about.