With the new 6.40 version I had a problem compiling it with BCB6.
The problem is in file sDialogs.pas, procedure Application_MessageBoxW, lines 232 and 234 : BCB6 doesn't know about Application.ModalStarted / ModalFinished.
I commented those two lines out, and it seems to work fine. So I guess there should be some kind of {$IFDEF COMPILER_VERSION} here.