A few days ago, Panasonic released firmware 2.3 for the Panasonic GH4, which contained the V-Log L profile upgrade.
While this firmware update gave you the profile, it could only be accessed with a key that you buy for $100 and gets mailed to you. Avoiding a download for the V-Log key was likely a way for Panasonic to try to keep this from getting hacked, but earlier today people did just that. If you've purchased the V-Log L key, when you get it in the mail, this is how you'll be installing it:
Matt Smith posted in our comments section a way to get this for free. This has been posted all over the web, but we won't be posting the instructions here. Essentially, if you want to get it to work on your camera, you'll need to have already installed firmware 2.3, and you'll need to use the Panasonic Image App. The firmware update is no longer available for download, and we don't condone anyone using this workaround who hasn't already purchased a key for V-Log L from Panasonic.
Apparently this update is causing issues with certain functions of the camera as well, like Zebras:
Anyone trying the V Log L workaround will notice Zebras & highlights working incorrectly. Get the real version 2B safe. @PanasonicProEU— Nick Driftwood (@NickDriftwood) September 16, 2015
Plenty of people have already done this and it works (I don't own a GH4, but know people who have them). I'm not sure how this was figured this out besides just experimenting, but to reiterate, if you haven't purchased the key legally, we can't support using this workaround. I'm sure Panasonic will release a new firmware that disables this ability, but in the meantime, if you've already installed the firmware, these instructions should work.