Actually hubiC doesn't want you to use its API unless you're a developer, which means you must pass the steps necessary to "create an application", after which you will be able to use all API calls. It's burdensome but doable.
hubiC makes it astonishingly hard for someone to create an app where a user just puts your account username and password and starts using it. If I was negative I'd say it's a scheme to prevent people actually filling their whole quota, because the only simple way they can do it is through the web ui or through the official syncing app.
Have you found a better alternative for duplicity backups?