Valve initially greenlit this mod back in 2017, and then went radio silent and just stopped communicating with the devs for 5 years before pulling this C&D.
The bootlicker mental gymnastics blaming the devs for valve not communicating or updating the SDK is infuriating when the TF2 mods that were barred on these grounds are currently in the process of being released on steam.
Their FAQ says they’ve never used any leaked code. It’s incredible that there are always people defending Valve for doing and being everything they otherwise hate.