Wolfire Games founder David Rosen claims they had "no choice" but to take legal action against Valve after the Steam creator allegedly began interfering with pricing on other storefronts. 

The Overgrowth developer filed an antitrust lawsuit against Valve in April after taking issue with the "extraordinarily high cut of revenue" it takes from Steam developers. The lawsuit also called out Valve for allegedly using Steam to create an "unassailable" monopoly on PC game distribution.

Now, Rosen has expanded on those allegations in a new blog post, claiming they "personally experienced the conduct described in the complaint."

"When new video game stores were opening that charged much lower commissions than Valve, I decided that I would provide my game Overgrowth at a lower price to take advantage of the lower commission rates. I intended to write a blog post about the results," wrote Rosen. 

"But when I asked Valve about this plan, they replied that they would remove Overgrowth from Steam if I allowed it to be sold at a lower price anywhere, even from my own website without Steam keys and without Steam’s DRM. This would make it impossible for me, or any game developer, to determine whether or not Steam is earning their commission."

Rosen goes on to allege that Valve made similar threats to other developers who charged lower prices on competing storefronts, telling them their titles would be pulled from Steam if they didn't raise their prices.

After taking issue with those actions, Rosen said they contacted a legal expert to check if Valve was actually obeying antitrust law, with those conversations ultimately resulting in the lawsuit that was filed last month. 

"As the dominant platform, when developers list their games on multiple PC stores, the majority of their sales will come through Steam. I believe this makes most developers afraid that if they don't sell on Steam, they will lose the majority of their revenue," they added.

"To those developers, avoiding Steam would add unacceptable risk to the already high risk of game development in general. I believe that most developers have little or no choice but to sell on Steam and do as they're told by Valve."

Those interested in the lawsuit can read Rosen's full blog post right here, though its worth keeping in mind Rosen's allegations are precisely that at this point.