Hello, I know your post is a bit old so I'm working with a 'better late than never' approach to this.

Passwords can now be extracted. Anyone who arrives here while looking for the solution, please be aware that with a bit of powershell knowledge, access to the DAC and administrative access to the local machine; you can use the following scripts (explained in the URL and downloadable from github) to get some of the passwords.

https://blog.netspi.com/decrypting-mssql-database-link-server-passwords/

Simon