Following a public dispute among Unity, Improbable and Epic Games about terms of service, Improbable and Epic Games are teaming up and announced a $25 million fund for game developers move to more open engines, services, and ecosystems.

The public quarel started when Improbable said in a blog post that Unity Engine games developed with Improbable's SpatialOS' cloud-based multiplayer Game Development Kit (GDK) are in violation of Unity's terms of service. Improbable said that Unity's decision to change its terms of service means the SpatialOS is essentially blocked from working with the Unity Engine.

Imporable's blog post shocked game developers, and Bossa Studios, the company behind Worlds Adrift and Spilt Milk Studios, said it had been contacted by Unity and told Worlds Adrift wouldn't be affected by the dispute. "Thus, Worlds Adrift remains live as normal," Bossa Studios said in a statement. "Our players are our priority and the Worlds Adrift team will be online on the typical channels to support them." Spilt Milk Studios said it would keep Lazarus (game) online until the game's servers were shut down "or we're told to turn them off."

Other developers working on games feared they would be forced to switch engines, wasting time and resources. Epic Games suggested the new Terms of Service could affect other online multiplayer games that don't rely on SpatialOS.

Unity later responded Improbable's blog post anc claimed that claims that it had told Improbable "more than a year ago" that it was violating Unity's terms of service. It followed up the warning in writing six months and then, two weeks ago, suspended Unity license keys held by Improbable employees. Unity also clarified that "projects that are currently in production or live using SpatialOS are not affected by any actions we have taken with Improbable." "If a game developer runs a Unity-based game server on their own servers or generic cloud instances (like GCP, AWS or Azure), they are covered by our EULA," Unity added.

It was then Improbable's turn to respond to Unity. In another blog post, shortly followed with a blog post, Improbable apologized for the "uncertainty, confusion and pain" developers felt throughout the day.

Finally, Epic Games, the company behind the immensely popular Fornite battle royale game, followed up: "Epic Games and Improbable would like to jointly reaffirm our commitment to giving game developers the best combination of engine and other technology backed by interoperable standards that work for everyone, while respecting developers' ability to choose partners and software components freely." Epic also announced a $25 million fund "to assist developers who are left in limbo by the new engine and service incompatibilities that were introduced today... [to] transition to more open engines, services, and ecosystems.The money will come from multiple sources including Improbable and the recently-launched Epic Games store," Epic said.

"Epic Games’ partnership with Improbable, and the integration of Improbable’s cloud-based development platform SpatialOS, is based on shared values, and a shared belief in how companies should work together to support mutual customers in a straightforward, no-surprises way," the engine maker wrote in a statement.

In a follow-up blog post tonight, Improbable wrote that "a commercial dispute between two companies (Unity and Improbable), in which both sides have certainly made errors, should never threaten access to essential technology used by a large number of developers. A world where this happens frequently will be a world with very little innovation in gaming."