Yes and No. Only one user can be registered to a Money Dashboard account. However, two people could agree to share the one account and it is possible to link the personal accounts of both parties and any joint accounts they may hold to the one Money Dashboard account. This is at the discretion of the users and there are security and privacy issues you should consider first. Both users would be able to see all the transactions on not only their joint accounts but all transactions on the other person's personal accounts too.
Alternatively both users can create their own Money Dashboard accounts which are both linked to the same joint accounts but only the individual's personal accounts.