Hello Michel,
In the current version of korganizer, there is a configuration option (in the settings -> Personal -> Use Groupware communication) where you can enable/disable these questions. If you enable groupware communication, you will be asked if you want to publish the event to the attendees. This works just fine here.

Cheers,
Reinhold

Created attachment 6452 [details]
KOrganizer Personal settings 

KOrganizer Personal Settings

Hello Reinhold,

The comments I made to the attachment were lost for some reason, so I am adding it now.
I am using the HEAD version of kdepim updated round =08h00 (swedish time) this morning. You can see my settings on the attached png. I could reproduce the bug. We definitly are _not_ asked to send an email to the attendees of a task.
To make sure before replying to you, I asked a colleague of mine to try on his on installation which is similar to mine and he could reproduce the problem too.
So I am pretty sure this those not work. Please revert the status of the bug if 
you agree with me or ask for more details if you need to know more, I will be happy to provide it to you.

Best,
Michel

Okay, Michel says it's not fixed, so reopen it...

CVS commit by kainhofe: 
 
 Editing a todo in the todo editor didn't send out groupware mails. The code was just missing... Copied from the event editor (I can't move that code to a method of the KOIncidenceEditor, because differnt functions need to be called for todos than for events). 
 
 CCMAIL: 82300-done@bugs.kde.org 
 
 
   M +40 -7     kotodoeditor.cpp   1.68 
 
 
 --- kdepim/korganizer/kotodoeditor.cpp  #1.67:1.68 
 @@ -41,4 +41,5 @@ 
  #include "koprefs.h" 
  #include "koeditorattachments.h" 
 +#include "kogroupware.h" 
  #include "kodialogmanager.h" 
   
 @@ -220,13 +221,37 @@ bool KOTodoEditor::processInput() 
   
    if ( mTodo ) { 
 +    bool rc = true; 
 +    Todo *todo = mTodo->clone(); 
      Todo *oldTodo = mTodo->clone(); 
   
 -    writeTodo( mTodo ); 
 - 
 -    mTodo->setRevision( mTodo->revision() + 1 ); 
 +    kdDebug(5850) << "KOTodoEditor::processInput() write todo." << endl; 
 +    writeTodo( todo ); 
 +    kdDebug(5850) << "KOTodoEditor::processInput() event written." << endl; 
   
 +    if( *mTodo == *todo ) 
 +      // Don't do anything 
 +      kdDebug(5850) << "Todo not changed\n"; 
 +    else { 
 +      kdDebug(5850) << "Todo changed\n"; 
 +      int revision = todo->revision(); 
 +      todo->setRevision( revision + 1 ); 
 +      if( !KOPrefs::instance()->mUseGroupwareCommunication || 
 +          KOGroupware::instance()->sendICalMessage( this, 
 +                                                    KCal::Scheduler::Request, 
 +                                                    todo ) ) { 
 +        // Accept the event changes 
 +        writeTodo( mTodo ); 
 +        mTodo->setRevision( revision + 1 ); 
      emit incidenceChanged( oldTodo, mTodo ); 
 - 
 +      } else { 
 +        // Revert the changes 
 +        todo->setRevision( revision ); 
 +        rc = false; 
 +      } 
 +    } 
 +    delete todo; 
      delete oldTodo; 
 +    return rc; 
 +   
    } else { 
      mTodo = new Todo; 
 @@ -234,6 +259,13 @@ bool KOTodoEditor::processInput() 
   
      writeTodo( mTodo ); 
 +    if ( KOPrefs::instance()->mUseGroupwareCommunication ) { 
 +      if ( !KOGroupware::instance()->sendICalMessage( this, 
 +                                                      KCal::Scheduler::Request, 
 +                                                      mTodo ) ) { 
 +        kdError() << "sendIcalMessage failed." << endl; 
 +      } 
 +    } 
   
 -    if ( !mCalendar->addTodo( mTodo ) ) { 
 +    if ( !mCalendar->addIncidence( mTodo ) ) { 
        KODialogManager::errorSaveTodo( this ); 
        delete mTodo;