Actually, the app should have an extension of .spl.
I just updated the file that is downloaded so it will have the proper extension. The downloaded file now is named:
spl_dashboard_examples.spl
This should fix the problem.
I renamed the file from spl_dashboard_examples.tar.gz to spl_dashboard_examples.tgz and now it works fine.
I have the same issue:
06-10-2013 09:48:22.024 -0700 WARN LocalAppsAdminHandler - There was a problem opening the archive at: /tmp/tmpLQ0qzC due to Unrecognized archive format
06-10-2013 09:48:22.024 -0700 ERROR LocalAppsAdminHandler - Error during app install: failed to extract app from /tmp/tmpLQ0qzC to /Users/503/splunk/var/run/72195639756dfdab: No such file or directory
Im on:
10.8.0 Darwin Kernel Version 10.8.0
Splunk 5.0.3 (build 163460)