When it comes to labels, by default, this function only loads current module labels into SUGAR.language.

These labels are acessible through the following command:

SUGAR.language.get('<ModuleName>', 'LBL_<LabelName>');

In order to add support to other module labels to be included, you should override _displayJavascript() method in your modules view, and specify which other modules labels should be included.

// modules/<ModuleName>/views/view.edit.php

require_once 'include/MVC/View/views/view.edit.php';

class <ModuleName>ViewEdit extends ViewEdit
{
    protected function _displayJavascript()
    {
        parent::_displayJavascript();

        if (!$this->_getOption('show_javascript')) {
            return;
        }

        $modules = array(
            '<Module1Name>',
            '<Module2Name>',
        );

        foreach ($modules as $module) {
            if (!is_file($GLOBALS['sugar_config']['cache_dir'] . 'jsLanguage/' . $module . '/' . $GLOBALS['current_language'] . '.js')) {
                require_once 'include/language/jsLanguage.php';
                jsLanguage::createModuleStringsCache($module, $GLOBALS['current_language']);
            }
            echo '<script type="text/javascript" src="' . $GLOBALS['sugar_config']['cache_dir'] . 'jsLanguage/' . $module . '/' . $GLOBALS['current_language'] . '.js?s=' . $GLOBALS['js_version_key'] . '&c=' . $GLOBALS['sugar_config']['js_custom_version'] . '&j=' . $GLOBALS['sugar_config']['js_lang_version'] . '"></script>';
        }
    }
}