Hi Antoine
As the app was required to be connected to Alfresco Cloud before the public API was created, we needed a way to access the non-CMIS APIs without opening this path up to everyone. Therefore, the store version of the app has this key at compile time in order to identify itself to the API gateway. We keep this key out of the source code to control access to this private channel.
I have asked Marc Dubresson to get in touch with you and we'll see if we can find a way to get you connected to cloud.
Thanks,
Mike