Linux system administrators tend to be minimalists, installing only the bare minimum of packages required to have a machine running. However, LiveCycle, depending on the Linux flavour, might require additional packages to be installed.
libcurl.so is a shared object (so) or library required by Forms ES and Output ES to merge XML data with form templates. cURL is a command line tool for transferring files with URL syntax, supporting HTTP and HTTPS, along with other protocols. If this package is not installed, testing of form rendering with XML data merge using FormsIVS will fail.
libidn.so is the Internationalized Domain Name support library, usually needed in non-English locales.
Xorg-x11-tools (for RHEL4) (Xorg-x11-apps for RHEL5)
These packages are required so that the LiveCycle installer as well as the LiveCycle Configuration Manager (LCM) Graphical User Interfaces (GUIs) can function.
Compatibility standard C++ libraries is yet another package that might need to be installed.