Has Stackfield been security audited and is the metadata safe?

It appears that Stackfield is one of the only functioning applications that combines end to end encryption, messaging services and file sharing. Peerio has just been launched (literally a day or two ago) so Stackfield remains interesting. I had two questions in this regard:

1. 
   

   Does anyone know if this application has been security audited and is there any review of its security features?

   
   


2. 
   

   Second, the Stackfield security page says this: "Only the so-called header data of the stack, i.e. the name and members of the stack remain unencrypted, because these need to be read for local search by name and by colleagues." This seems to imply that the metadata, i.e. who is working with whom, is in the clear. Would this be a correct interpretation?