Ladies and gentlemen, the mobile OS war is getting into high gear, and apart from iOS, Android and Windows Phone, we have yet another contender intent to take the smartphone world by storm. This time, it’s Chinese e-commerce giant Alibaba. And with the Chinese smartphone market set to become the biggest in the world, it’s no wonder platform-makers and manufacturers want a big slice of this pie.

But there was a big uproar last week when Acer’s planned announcement of an Aliyun-powered smartphone was cancelled at the last minute. Google drew some flak for allegedly bullying Acer into pulling the plug on its Aliyun smartphone development. Andy Rubin, senior VP for mobile and digital content at Google, basically said that Acer could not work on an Android fork because of its membership in the Open Handset Alliance. If it does decide to work on an Android fork, then Google will no longer support Acer in its Android smartphone (and tablet) efforts.

Alibaba took offense, and has issued a response to Rubin’s comments. In an interview with CNet, John Spelich, VP for international corporate affairs at Alibaba, said Aliyun is not an Android fork, and has stressed that “Aliyun is different.”

Spelich stated that Aliyun is “built on open-source Linux,” and that Alibaba has its own applications. “[It’s] designed to run cloud apps designed in our own ecosystem. [It] can run some but not all Android apps.”

Google’s point of contention is that Aliyun uses some of Android’s SDKs. Spelich continues:

Aliyun’s runtime environment, which is the core of the OS, consists of both its own Java virtual machine, which is different from Android’s Dalvik virtual machine, and its own cloud app engine, which supports HTML5 web applications. Aliyun OS uses some of the Android application framework and tools (open source) merely as a patch to allow Aliyun OS users to enjoy third-party apps in addition to the cloud-based Aliyun apps in our ecosystem.

Spelich further criticized Android for not actually being open, because of the way the platform distributes content through apps, which means the platform-maker essentially acts as gate-keeper to this content.

[W]e are an ecosystem that includes other Internet companies, whereas Android does not because it provides apps through downloads. It’s the crux of the whole cloud vs. app debate. Cloud is open, apps system is closed because it is controlled by the operator of the apps marketplace.

Andy Rubin has replied, this time pointing out that Aliyun uses elements from Android and even contains pirated Google apps.

Hey John Spelich — We agree that the Aliyun OS is not part of the Android ecosystem and you’re under no requirement to be compatible.

However, the fact is, Aliyun uses the Android runtime, framework, and tools. And your app store contains Android apps (including pirated Google apps). So there’s really no disputing that Aliyun is based on the Android platform and takes advantage of all the hard work that’s gone into that platform by the OHA.

So if you want to benefit from the Android ecosystem, then make the choice to be compatible. It’s easy, free, and we’ll even help you out. But if you don’t want to be compatible, then don’t expect help from OHA members that are all working to support and build a unified Android ecosystem.

Which is which? Is Aliyun indeed an independent Linux distribution that only borrows SDKs from Android, and as such cannot be called an Android fork? Or is the inclusion of “runtime, framework, and tools” enough to mean Aliyun is actually an Android fork and would result in Acer violating the terms of its membership into the OHA if it decided to launch an Aliyun OS phone?