Relaunch us required for the library restore to take effect"
This probably means, that the restored library needs to be upgraded to the new version. Simply hit o.k. and proceed.
If this will not work, post back.
Hat tip to Léonie, that's correct. You can restore your library from a vault, even if you don't have the original library anymore. If the vault is from an earlier version of Aperture it is a two-step process: First restore the library from the vault, then upgrade the library to the latest Aperture. The "Relaunch" dialog is presented when Aperture is ready to upgrade the restored library. Simply quit and relaunch Aperture and your library should be restored, upgraded and ready to work with.
The step-by-step process:
1. First, create a new library in the latest Aperture, then select File > Vault > Restore Library and choose the vault from the File IO dialog. Aperture will restore the original library, then present the Relaunch dialog indicating it's ready to upgrade the restored library to the latest version.
2. Quit and relaunch Aperture. Your library should be restored.