applydeltarpm is a process internal to yum, which is OpenSUSE's package manager on top of RPM (also Fedora's and other RPM based distros).
The job of applydeltarpm is to reduce network load:
Instead of downloading the full RPM files from the repositories, special Delta-RPM files (.drpm) may be available, that are just a fragment of the download size. In order to construct the real rpm file to be installed by RPM, applydeltarpm takes the old cached rpm in your filesystem and applies the delta-rpm on top of it. This process is CPU-intensive, and that's why you have a high load during that phase.
If you have a broadband connection and tiny batteries and/or you would rather consume bandwidth than CPU, then you can adjust yum's behaviour to when to download delta-rpms.
Depending on your Package Manager, you'll have to edit its configuration file.
In OpenSUSE, assuming you're using zypper:
There's a configuration option in /etc/zypp/zypp.conf called download.use_deltarpm which can be set to false. (Taken from [1])
In Fedora, or assuming you're using yum:
There's a configuration option in /etc/yum.conf (see yum.conf(5)) called deltarpm_percentage that adjust how smaller has the delta-rpm to be to download it instead of the full rpm.