Adding captcha to your forms using hooks are possible. Works with following captchas.
<?php
function my_component_captcha_add(){
ossn_add_hook('captcha', 'protected:components', function($hook, $type, $captcha, $params){
if(!is_array($captcha)){
$captcha = array();
}
//examples
//your form names
$captcha['protected_forms'][] = 'login';
//actions
$captcha['protected_actions'][] = 'user/register';
return $captcha;
});
}
ossn_register_callback('ossn', 'init', 'my_component_captcha_add');