I'm not aware that DL has even started doing anything in BOS with D1 lounge as I haven't seen any activity upstairs from the terminal concourse, unless they changed their mind and will stick it in the basement area where the old business lounges were.

Supposedly the BOS D1 lounge is going to be connected to the existing terminal E skyclub... not sure where but maybe off to the right of the entrance past the bathroom and shower area.