Yank works in OS X 10.2 or later. That means it works in Jaguar, Panther or Tiger.
Yank requires OS X 10.4 (Tiger) or later to create Yank files. It cannot create Yank files in Panther or Jaguar. Yank also cannot create Yank files in user accounts protected by File Vault.
If your system prevents you from creating Yank files, you can still use Yank to run Yank files that other people create.