Server download error message not helpful: 'Unknown response code: 503'

1. From JBoss Central click HTML5 project.
2. In wizard, under Requirements, select 'This project example requires JBoss Enterprise ...' and click 'Download and Install'.
3. From list, select JBoss EAP 6.2.0 and click Next.
4. In fields type username and password and click Validate.
>> window showed 'Unknown response code: 503'

Not sure what this error is for - server timeout? [I assume it wasn't for wrong password or unknown username as these result in the 'Your credentials are incorrect.' error message.] This 503 error message only happened once - on subsequent try all worked fine. But the error message needs improving if it is going to be helpful to users.