api key vs password for wpmudev dashboard and updates

I remember when it used to be possible to get updates with the API key. I am considering using WPMU premium plugins on a client site, but I do not want to give them username/password information to my wpmu account. How can I use my gold membership to install plugins on this new site without giving them my password info? The dev dashboard only appears to have a spot for username and password, and no longer has a spot for API key.

what is considered best practice here.