You can run TheRecipeManager under different accounts on OS X. However, you can only actually run one 'Instance' of TheRecipeManager. So if you switch users without quitting TheRecipeManager, then it will not run when you change to a different user. The first time that you run the program under each different user, you will need to license the program again.
By default, each user will have their own recipes data file, and any additions made to one will not automatically show up in the other. If you wish to maintain separate datafiles and want to share recipes, you'll need to export recipes, and then import them into the other user's collection, after they've logged in.
Like most software licensing, the licensee can use TheRecipeManager on two different Machines, so long as the use is not simultaneous.