Two of the most popular mods for Team Fortress 2 have been taken down this week, with both TF2 Classic and Open Fortress being removed due to "an arrangement" with Valve.
According to almost identical tweets from the Twitter accounts of both mods, the removal is simply "due to an arrangement with Valve," and that there will be some "temporary disruption" if which players have "nothing to be worried about" - whatever that means.
Downloads for Open Fortress are currently suspended due to an arrangement with Valve. This suspension is temporary and we will keep you informed on future developments as they come - stay tuned!— Open Fortress (@OpenFortress) September 10, 2021
It could represent an official Steam page for both mods, or they could be turning into official features in the base game, although it's difficult to know right now. Valve is usually very friendly to modders, with examples such as Black Mesa going from being a mod for Half-Life 2 to its own, fully-fledged licensed game.
We'll be sure to keep an eye on the situation and let you know as soon as we learn anything further.