This game appears to be an IPB game but the package doesn't have the "gamedata" directory so the importer failed to recognized it as an IPB game package. If in the import page, you choose IPB as the system and just click import, it will happily go ahead and read the game title, description, etc...
IIRC, the files are copied to internal_data before being added by the install script (have to be done because the data writer will delete the file after a successful insert). I will do a fresh install in the evening and report back.
Yeah, the TAR extraction is handled by Zend Framework (which comes with XenForo). Not sure why it doesn't work correctly for you. Let's wait for a while to see if anyone else get the same problem.
Looks good to me. Can you ask the admin to put the test script in XenForo directory and run it from there? Just to make sure php.ini is not somehow overridden in your installation directory.
I think the include_path is not configured correctly in your php.ini file. Please contact your server administrator to check on that. Alternatively, you can send your server SSH information via conversation, I will login and check for you.