wp-plugin.php error on line 27

Luckily there is a simple fix for this. You need to swap the order of some of the functions around in recaptcha.php and wp-plugin.php.

In both files, the function __construct block should come before the function that shares the same name as the class. For example, recaptcha.php had been looking like this:

class ReCAPTCHAPlugin extends WPPlugin
{
    private $_saved_error;
    private $_reCaptchaLib;

    /**
     * Php 4 Constructor.
     *
     * @param string $options_name
     */
    function ReCAPTCHAPlugin($options_name) {
        $args = func_get_args();
        call_user_func_array(array(&$this, "__construct"), $args);
    }

    /**
     * Php 5 Constructor.
     *
     * @param string $options_name
     */
    function __construct($options_name) {
        parent::__construct($options_name);
        $this->register_default_options();

        // require the recaptcha library
        $this->_require_library();

        // register the hooks
        $this->register_actions();
        $this->register_filters();
    }

But will now need to look like:

class ReCAPTCHAPlugin extends WPPlugin
{
    private $_saved_error;
    private $_reCaptchaLib;

    /**
     * Php 5 Constructor.
     *
     * @param string $options_name
     */
    function __construct($options_name) {
        parent::__construct($options_name);
        $this->register_default_options();

        // require the recaptcha library
        $this->_require_library();

        // register the hooks
        $this->register_actions();
        $this->register_filters();
    }

    /**
     * Php 4 Constructor.
     *
     * @param string $options_name
     */
    function ReCAPTCHAPlugin($options_name) {
        $args = func_get_args();
        call_user_func_array(array(&$this, "__construct"), $args);
    }

Make sure you make the same type of change to wp-plugin.php too.