Unity Engine games developed with SpatialOS' cloud-based multiplayer Game Development Kit (GDK) are now in violation of Unity's terms of service, according to SpatialOS maker Improbable. The decision imperils the operation of many in-development game projects, including some that have already been released to the public.

Since its open beta release in 2017 (in partnership with Google), SpatialOS has allowed developers to easily integrate mass-scale multiplayer into their games by running a persistent version of the game in the cloud. But Improbable now says that a recent change in Unity's terms of service means the SpatialOS is essentially blocked from working with the Unity Engine.

The newly updated clause 2.4 of the Terms of Service now specifically excludes "managed service[s] running on cloud infrastructure" which "install or execute the Unity Runtime on the cloud or a remote server." Though the terms of service were changed on December 5, Improbable says Unity confirmed directly to them this week that the update "specifically disallow[s] services like Improbable’s to function with their engine. This was previously freely possible in their terms, as with other major engines."

As a result, Improbable says, "this change effectively makes it a breach of terms to operate or create SpatialOS games using Unity, including in development and production games." That list of imperiled games includes Bossa Studios MMO Worlds Adrift, VR MMO MetaWorld, and Klang Games' upcoming MMO Seed, among others.

Improbable says the ToS change comes as the company was actively negotiating with Unity "to find a way to do more together." Improbable also says it is continuing to talk to Unity in an effort to reverse the decision, though its license to work with the Engine has currently been revoked. A Unity representative was not immediately available to respond to a request for comment.

"Overnight, this is an action by Unity that has immediately done harm to projects across the industry, including those of extremely vulnerable or small-scale developers and damaged major projects in development over many years," Improbable says. "Games that have been funded based on the promise of SpatialOS to deliver next-generation multiplayer are now endangered due to their choice of game engine. Live games are now in legal limbo."

Improbable is promising to "do everything in our power to help developers using SpatialOS with Unity to finish, release, and operate their games," including using an emergency fund to help with developers' finances, releasing the Unity GDK as an open source project, and assisting in porting to new engines as a last resort.

"SpatialOS [has made] it easier [for me] to build large-scale multiplayer games using a cloud-based solution," developer AtomiCal writes on the Unity forums. "Today I woke up to a message essentially pulling the rug from under my feet saying that I can't do that anymore. Unity won't let it happen."

We'll update this story as we hear back from Unity and any other developers affected by this decision.

Update: Bossa Studios Head of Marketing Daniel King tells MCV "Bossa’s main priority is our players. Whatever is happening in the background is outside of our control, our focus is ensuring the players are looked after and their memorable experiences in the game are protected. For now, Worlds Adrift is operating as normal."

Update 2, 6:26 pm ET: Unity has officially denied Improbable's allegations. In a lengthy blog post on the matter, the game-engine company offered a clarification for any Unity game makers concerned about their use of SpatialOS: "Projects that are currently in production or live using SpatialOS are not affected by any actions we have taken with Improbable," the blog post says. "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."

You'll have to scroll through the entire blog post to find Unity's version of the Unity-versus-Improbable story: "If a third-party service wants to run the Unity Runtime in the cloud with their additional SDK, we consider this a platform. In these cases, we require the service to be an approved Unity platform partner." This, Unity alleges, was the sticking point in a negotiation process that went on for "over a year" with Improbable. Unity claims it sent formal, written notice of this ToS violation to Improbable "six months ago." Unity adds that "game developers should never pay the price" for Improbable's "violation" of the Unity EULA, and as a result, "games currently in production and/or games that are live [with use of Improbable's tech] are unaffected."

Update 3, 10 pm ET: Unreal Engine maker Epic Games and Improbable have teamed up to announce a $25 million fund that they say will "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 for this fund will be drawn from "Unreal Dev Grants, Improbable developer assistance funds, and Epic Games store funding" among other sources, 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.

While Unity maintains that its ToS update does not actually imperil SpatialOS games and that its disagreement with Improbable stems from separate license negotiations, it seems the damage to the relationship between the two companies has been done. In a follow-up blog post tonight, Improbable writes that "a commercial dispute between two companies, 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."

Update 4, 3:30 pm ET, Jan. 11: In what Improbable is describing as its "final statement" on its conflict with Unity, the company says it had been assured by Unity that SpatialOS was compliant with the Unity Terms of Service as they existed before December 5. A ToS update on that date, though, means that "any managed service like SpatialOS, or user of a managed service, risks being in breach of this license term," the company says.

Improbable says its public message yesterday was in response to its own license to the Unity Engine being revoked over this ToS violation. Though Unity has since offered an "exception" that will allow existing SpatialOS releases and in-development Unity projects to continue operating, Improbable maintains that "at the point they asserted on 9 Jan that we were in breach, our service could not legally run."

With its Unity license still suspended, Improbable says it "cannot easily fix bugs, improve the service or really support our customers without being in a legal grey area. Anyone who has ever run a live game knows this is a farcical situation that puts games at risk. Unity has still not clarified this, granted an exception or had a conversation with us, but we hope this will change."

Improbable continues to ask for clarification of Unity's terms of service and the reinstatement of its engine license. "Our preference would be that Unity simply adopts industry standard practice and allows platforms to host the engine as was the case before the change in Terms of Service," it writes. "Failing that, Unity must grant Improbable sufficient legal basis to protect its existing customers, or be honest with the community about the situation."