"You will receive a password and account designation upon completing the Service's registration process. You are responsible for maintaining the confidentiality of the password and account and are fully responsible for all activities that occur under your password or account. You agree to (a) immediately notify Yahoo! of any unauthorized use of your password or account or any other breach of security, and (b) ensure that you exit from your account at the end of each session. Yahoo! cannot and will not be liable for any loss or damage arising from your failure to comply with this Section 5."
What I take from this is that Yahoo explicitly does not say that you can expose your password or id to anyone. What it implies is that if you do then you must act responsibly.
So for example, if you write your password down on a piece of paper and stick it next to your computer you must decide if that is acting responsibly. If you tell a partner, relation or friend your password then you must decide if that is a responsible thing to do.
Similarly if you enter your password into a secured and encrypted system such as Grouply then you must personally decide if that is a responsible thing to do. The emphasis is on what you personally decide.
Also did Grouply ask your for authorisation for your password? Is that in their terms and conditions?
So you must decide if Grouply is a bona-fide company. You can do this by checking its legal status. You can also check its investors out. You can also ask whether Grouply stores the password securely. Also does Grouply keep you in full control of your password at all times, including the possibility to delete or change it. Finally is Grouply's approach to privacy backed by any independently verifiable process.
If the answer to all of these is positive then is there anything more that you could do? If the answer is that you have covered all bases, then surely you have acted responsibly. On this conclusion would I argue that using Grouply is a safe thing to do.
