Okay, released 5.3.3 with a fix for this.
@Peter there is no issue with displaying the site-key - it's there for exactly this purpose - to display it to everyone. What you shouldn't display is the secret key.
@Jean -> there is a better way to display the captcha now:
<?php
$captcha = JCaptcha::getInstance(HotspotsHelperSettings::get('captcha'));
echo $captcha->display('compojoom-captcha', 'compojoom-contact-captcha', 'g-recaptcha');
?>
With this code you should be able to use any captcha plugin and not just google's recaptcha.
Cheers,
Daniel