Here's a response from DYMO. I asked about Mavericks compatibility with certain LabelWriter models (my workplace has several - 330s to 450 Turbos).
The LabelWriter series 400 and 450 are compatible with the Maverick, provided you have installed DymoLabel software 8.5.1.
The LabelWriter 330 series has models that are compatible and some that are not. If the 5 digit model number on the bottom of the 330 is 90884, 93033, 93038, 90891 or 93037 (USB models only), should also be compatible with Maverick and our 8.5.1 software.
Installation instructions for 8.5.1 follow:
Before the latest software release, DymoLabel software was not fully compatible with all Mac operating systems.
It is important that you uninstall any Dymo printer and software and do a clean installation of the latest DymoLabel software for your Mac.
If you are upgrading to Version 8 of the DymoLabel Software and currently have an earlier version, we suggest that you back up your addressbook prior to installing this software. (If this is your initial installation, you can skip this backup step.)
The back-up instructions can be found here:
https://dymo.custhelp.com/app/answers/detail/a_id/2331/kw/2331
The steps to install the latest DymoLabel Software (DLS) follow. All steps are important.
1. Go into System Preferences> Print and Scan and delete the DYMO printer. Then, unplug the USB cable for the printer.
2. Go into your applications and drag the DYMO Label application into the trash.
3. Browse to Macintosh HD> Library> Frameworks> DYMO, and delete that DYMO folder.
4. Browse to Macintosh HD> Library> Printers> DYMO, and delete that DYMO folder.
5. In the Finder, click on 'GO' in the toolbar at the top of the screen, then hold down the Option key on the keyboard. A new Library menu option will appear in the 'GO' menu. Click on Library > Preferences, and delete any com.DYMO files.
6. Empty the trash then restart the computer.
7. Once restarted, install this version of the DYMO software:
http://download.dymo.com/dymo/Software/Mac/DLS8Setup.8.5.1.dmg
8. Once installed, plug the printer back in and it should automatically be recognized.
9. Open the software and try to print.
NOTE: Do not connect the USB cable to your computer or USB hub until instructed to do so during the software installation. If you have a label printer already installed, disconnect the USB cable from your computer before running the installer and reconnect the cable when instructed to do so.
Connect the USB printer cable into a USB port directly on the computer. It will not work if connected to a USB hub, docking station or Mac keyboard.
Please let us know if we can help you further.
You can also reach us by telephone, if that is more convenient, at 877-724-8324, Monday - Friday, 8AM - 7PM EST, for further troubleshooting.
I hope this helps.