First of all, this is a customer-to-customer forum and, while DreamHost staff drops in from time to time, they rarely post here and this is not a way to contact DreamHost support or administrative staff. I do not know the circumstances involved , but if the account was "disabled" for abuse, fraud, or illegal activity, you should understand that the DreamHost Support staff will most likely not be the ones handled the matter.
While support does work 24/7/365, such matters are normally handled by the Abuse Department staff, which is much smaller and works a different schedule. Being that this is the weekend in the U.S., and many office staff members do not work on those days, you may need to wait until the business week begins on Monday morning (PDT) for those handling your issue to be available.
Edited for new information:
Though I speak little Chinese, I think it is pretty obvious that there is a least some indication that abuse was alleged to be involved in the disablement and that there has been at least some discussion of fraud. This leads me to believe that the Technical Support people normally available on weekends will probably not be responding to your Support tickets, and have likely forwarded your Support tickets to the Abuse staff for further attention/resolution.
No one here can help you with any of this, and this is not really the appropriate place for such discussion.
It sounds to me that you may be a little confused by the language. Generally speaking, ""take your business elsewhere" doesn't leave even a "mere possibility" of turning the account "alive" - it usually means "we do not want to do business with you, go away".
Different people see different things as "reasonable". The DreamHost Terms of Service is designed to make sure that everyone understands what is "reasonable", what they can expect from DreamHost, and their responsibilities in handling their account.
It is the account holders' responsibility to back up any data that they cannot afford to lose, and DreamHost has no obligation to allow access to a suspended/disabled/deleted account for the purposes of retrieving data left on a DreamHost server.
This is the wrong place to attempt to resolve such an issue. If "Flavien" is the account holder, he should contact DreamHost via the Control Panel Support Request mechanism, if he still has access to the Control Panel via his WebID. If he no longer has such access, he might try the contact form at http://dreamhost.com/contact.cgi.
It seems that you are trying to help your friend, and that is admirable, but you should understand that your status as a "privileged" user on the account is not likely to allow DreamHost to deal with you regarding this matter. I suspect that they will need to deal with Flavien, if he is the account holder, as it is the account holder with whom DreamHost has a business relationship.
All that said, your request for the data is politely and graciously worded. Should Flavien send such a request to DreamHost he may, or may not, be able to get some help in this matter. You should know, however, that if the "stuff" is "illegal material" (see http://www.abuse.dreamhost.com), it is highly unlikely that DreamHost could provide you with copies of that material without breaking the law themselves by doing so.
It is really important to back up anything you consider to be important or valuable if whenever you store it on any computer. While this is true with regards to all computers, it is especially true regarding computers that do not belong to you.