$ sudo aptitude install kde-zeroconf-kde4                                                              
Reading package lists... Done                                                                                         
Building dependency tree                                                                                              
Reading state information... Done                                                                                     
Reading extended state information                                                                                    
Initializing package states... Done                                                                                   
Building tag database... Done                                                                                         
The following NEW packages will be installed:                                                                         
  kde-zeroconf-kde4                                                                                                   
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.                                               
Need to get 0B/34.1kB of archives. After unpacking 172kB will be used.                                                
WARNING: untrusted versions of the following packages will be installed!                                              

Untrusted packages could compromise your system's security.
You should only proceed with the installation if you are certain that
this is what you want to do.                                         

  kde-zeroconf-kde4 

Do you want to ignore this warning and proceed anyway?
To continue, enter "Yes"; to abort, enter "No": yes   
Writing extended state information... Done            
Reading package fields... Done                        
Reading package status... Done                        
Retrieving bug reports... Done                        
Parsing Found/Fixed information... Done               
(Reading database ... 239207 files and directories currently installed.)
Unpacking kde-zeroconf-kde4 (from .../kde-zeroconf-kde4_4%3a4.0.98-0ubuntu1~hardy1~ppa1_i386.deb) ...
dpkg: error processing /var/cache/apt/archives/kde-zeroconf-kde4_4%3a4.0.98-0ubuntu1~hardy1~ppa1_i386.deb (--unpack):
 trying to overwrite `/usr/lib/kde4/lib/kde4/kio_zeroconf.so', which is also in package kdnssd-kde4                  
Errors were encountered while processing:                                                                            
 /var/cache/apt/archives/kde-zeroconf-kde4_4%3a4.0.98-0ubuntu1~hardy1~ppa1_i386.deb                                  
E: Sub-process /usr/bin/dpkg returned an error code (1)                                                              
A package failed to install.  Trying to recover:                                                                     
Reading package lists... Done                                                                                        
Building dependency tree                                                                                             
Reading state information... Done                                                                                    
Reading extended state information                                                                                   
Initializing package states... Done                                                                                  
Building tag database... Done