Error creating Mavericks bootable usb key

The command shown is incomplete. We need to see the entire command being issued. The command in the picture ends at "--applic", but should be:

--applicationpath  /Applications/Install\ OS\ X\ Mavericks.app

Either post a full screenshot of the Terminal window, or copy & paste the command & messages into the "Code Insertion" tool on the forum editing toolbar which looks like "<>".

Is macOS fully patched on the system where you are attempting to run this command? How did you acquire this Mavericks installer? And what is the exact model of the Mac being used to make the USB installer? You can get the exact model by clicking the Apple menu and selecting "About This Mac".

Edit: Also, are you booted into a full version of macOS when attempting to create the bootable USB installer? It may not be possible to do this from Recovery Mode or while booted from a macOS installer as those environments are extremely limited.

Hello Pier-Alexis,

Welcome to Apple Support Communities. 

We understand that you want to create a bootable installer with OS X Mavericks. We are happy to help.

Here’s the resource to download OS X Mavericks: Download OS X Mavericks 10.9.5 Update (Combo)

We recommend using the steps here to create a bootable installer: Create a bootable installer for macOS - Apple Support

"What you need to create a bootable installer

• USB flash drive or other secondary volume with at least 14GB of available storage, formatted as Mac OS Extended.
• Installer for OS X El Capitan or later. To get the full installer, your Mac must be using the latest version of OS X El Capitan, the latest version of macOS Sierra, or any later version of macOS. Download from a Mac that is compatible with the macOS you're downloading. Enterprise administrators: download from Apple, not a locally hosted update server.

Use Terminal to create the bootable installer

1. Plug in the USB flash drive or other volume that you're using for the bootable installer. 
2. Open Terminal, which is in the Utilities folder of your Applications folder.
3. Type or paste one of the commands below into Terminal, then press Return to enter the command. Each command assumes that the installer is in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If the volume has a different name, replace MyVolume in the command with the name of your volume.
4. When prompted, type your administrator password. Terminal doesn't show any characters as you type. Then press Return.
5. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the volume is erased.
6. After the volume is erased, you may see an alert that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed. 
7. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Monterey. You can now quit Terminal and eject the volume."

Let us know if you have further questions.

Take care.