Two popular FPS game's developer.
Both teams say that they closed their mods for the multiplayer game down after receiving an email from Valve asking them to suspend operations. According to both development teams, discussions were underway to bring the projects to Steam as officially-recognised mods. However both say that they've heard no from Valve since the initial discussions, despite attempting to them on multiple occasions through several different avenues of communication.
Eminoma Team, the creators of TF2 Classic, a mod aiming to recreate the feel of the game during its first year, posted a lengthy statement to the mod's website talking about the difficulties they have faced over the downtime. The team states: "On March 10, around six months after their last reply, we decided to send a final email announcing that we plan on opening our s back up until they re-affirm that they want us to keep them down. So our reasons for reopening are due, in short, to the lack of response from Valve."
The Open Fortress team, who created an arena-style shooter mod in the vein of Quake using TF2's codebase and art style, posted a shorter blog titled 'Welcome back,' which addressed similar concerns. They also spoke to Valve's radio silence, stating that, "After some time had ed we never really got a response back from them. We waited, thinking that they would eventually get back to us, but they never did."
With the recent news of Valve responding to the #SaveTF2 campaign following a community protest from fans looking for any sign of for the popular game, hearing that two big mod creation teams have been left in the dark by Valve for the past year will certainly cause concern for some.