Assuming a package is defined in this way:

  <pack name="Core Files" required="yes" id="core.package">
    <description>The core files required for this application</description>

the according name and description can be translated in the installer in the following way:

First, define a package translation file per language, for example german:

  <str id="core.package" txt="Anwendungs-Kern"/>
  <str id="core.package.description" txt="Unbedingt notwendige Dateien für das Betreiben dieser Anwendung"/>

and add them as packsLang.xml_<LANGUAGE_CODE> to the installation descriptor:

  <res id="packsLang.xml_eng" src="i18n/packsLang.xml_eng"/>
  <res id="packsLang.xml_deu" src="i18n/packsLang.xml_deu"/>