You can use above code anywhere in your template to render the form.
Though registering the form on/before bp_init action may seem like a bad choice to some of you, It allows for server side validation of the credentials/authentication and thus helps from any misuse of the form.
It is a free plugin, please feel free to download it and use it on your custom projects. The Blog Categories for Groups & BuddyBlog plugin supports this plugin. You will simply need to activate this plugin and the plugin will work as the form handler for the BuddyBlog/BCG.