The developers are vetoing ReShade

At the start of the Early Access PlayerUnkown himself has granted the users to play the game with the third party software program ReShade which with some knowledge and patientce could be turned into a powerful tool that allowed players to see other objects more clearly, however sacrificing a bit of fps. Since that time many people got addicted to it and now they probably can't experience the game without it. But it looks like the developer team have changed their mind in the current patch, that was uploaded on live servers today, the battleye anticheat is banning all third party software.

Here is the statement from the community coordinator.

PUBG_RoboDanjal:

We are testing a new anti cheat solution on our test servers this week and it is to block cheats more effectively. This will also block 3rd party programs that modify the gameplay or visuals in an invasive way. Reshade is one of the programs that will be blocked by this measure.
We are first testing the anti-cheat solution on our test servers. Patch Notes  Launch/Crash reporting
When this is implemented on the live servers, such programs will be blocked. We will provide more updates when they become available.

 Many of the current ReShade users will find this decision most dissapointing, however if it helps to reduce the amount of cheaters in the game it would be a good measure.

Origin: forums.playbattlegrounds.com