This basically adds Windows 98 connection functionality to Windows 95. It is still too soon for a proper assessment. DUN13 is packaged with Windows 98 and appears to be satisfactory. Version 1.3 may also be very difficult to uninstall fully - be prepared to remove the entire comms package if you find it unsatisfactory. If DUN12 is working correctly then perhaps you should stay with it for now.
Caution is advised for the time being.
If you install it or have Win98, then look in Control Panel Network Dailup adapter and set the Packet Size to small which sets it to 576 . It also installs a ws2relnotes.htm which you should read. It must only be used with DUN13.