I asked for a key, and was given one instantly... used it with hubic to openstack gateway[1] and works very well
Of course it's easy for you because you understand what a client id and a client secret are, and you know why they differ from your username and password. I'm talking about the average Joe that barely knows what a URL is, a redirect URL even less. You know what openstack means, and you know what a gateway is and can run one.
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.
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.