Considered all the issues that have been raised by QLC+ users around this topic, here's an extract of the official FTDI Application Note 134

# Disabling the Apple-provided VCP on OS X 10.9 and later

A VCP driver for most FTDI USB to serial converters is provided as part of the kernel in OS X 10.9 and later. OS X loads this driver (AppleUSBFTDI.kext) when a device with standard FTDI vendor and product identifiers is connected. To use FTDI's own VCP instead, or to use D2XX programs, AppleUSBFTDI must be disabled, unloaded or blocked, as follows.

## Disable by Renaming (OS X 10.9 and 10.10 only)

Note: this method works only on 10.9 Mavericks and 10.10 Yosemite.
Start a terminal session (Go > Applications > Utilities > Terminal) and copy/paste the following text to the command prompt:

    cd /System/Library/Extensions/IOUSBFamily.kext/Contents/Plugins
    sudo mv AppleUSBFTDI.kext AppleUSBFTDI.disabled
    sudo touch /System/Library/Extensions

then reboot.
To re-enable VCP, rename AppleUSBFTDI.disabled back to AppleUSBFTDI.kext

    cd /System/Library/Extensions/IOUSBFamily.kext/Contents/Plugins
    sudo mv AppleUSBFTDI.disabled AppleUSBFTDI.kext
    sudo touch /System/Library/Extensions

then reboot.

## Temporarily Unload (all versions of OS X)

Note: this method works on all versions of OS X.
It is possible to unload Apple's VCP for the current session, i.e. until the next reboot:

    sudo kextunload -b com.apple.driver.AppleUSBFTDI

(If a warning message indicates that the kext can't be unloaded, then reboot and retry the above command.) To reload:

    sudo kextload -b com.apple.driver.AppleUSBFTDI

The kextunload and kextload commands can be run in any directory.

## Block with D2xxHelper (OS X 10.9 and later)

Note: this is the only non-temporary method which works on 10.11 El Capitan.
FTDI provides a signed kernel extension (D2xxHelper.kext) which contains no code but acts to prevent OS X from matching an FTDI chip (with standard vendor and product identifiers) with a VCP driver, either Apple's or FTDI's. This leaves the device unclaimed, and available for D2XX programs only.
1. Disconnect all FTDI devices.
2. Download and run the D2xxHelper installer from https://www.ftdichip.com/Drivers/D2XX.htm
3. Reboot.
4. Reconnect the FTDI devices.