There is an interesting discussion in The Guardian about English-speaking playwrights taking foreign-language plays in the public domain and rewriting them under their original names. Now we're not talking about adding incidental music to something or updating a idiom to cross cultural and historical barriers. The changes cited would be akin to allowing Hamlet and Ophelia to live while still calling the adaptation "Hamlet."
As always there are two sides to this debate. Respect for the author and what he has written is the first and quite clearly definable side of the argument. The other can fall along the lines of citing theater's inheritance collaborative process and the shortening attention spans of modern audiences. But I think the real discussion needs to be had around why the changes were felt to be necessarily in the first place - and why not write your own play instead of reviving an old one.
I have seen plenty of productions that completely overhaul the play without changing the title and thoroughly enjoyed them. I've seen others that are utterly miserable experiences.
Elia Kazan (1909-2003)