Dawoodi Bohra Forum

I've noticed that books on the Dawoodi Bohras (except some recent work by Blank) are quite difficult to get a hold of, particularly the Gulzare Daudi of Abdul Hussain - though other recent work (e.g. The Bohras) is almost as difficult.

Having finally acquired a copy of GD, how does one determine whether copyrights have expired and whether it would be ok to make the book available in pdf form in the public domain?