Code samples for the Box API are now uploaded to GitHub. You can find them here: https://github.com/HPInc/printos-box-api-samples
That URL is only intended for API submissions into the Box application. If you're trying to browse to that URL with a web-browser it won't work. If you're having issues with one of the code samples, or submitting orders into Box over the API please let me know what the error message you're receiving is and we can help to resolve the issue.
Also, you will need an active PrintOS account or valid Key/Secret from an existing account in order to use the API.