Microsoft’s fledgling mobile operating system, Windows Phone 7, managed to be live for little over a month before somebody released a jailbreak tool for the OS. Three men have just done that, as Rafael Rivera, Chris Walsh and Long Zheng put out the ChevronWP7 yesterday, an executable file that allows users to sideload apps to a Windows Phone 7 phone – making it possible to install software on the devices without going through Microsoft‘s official Windows Marketplace.

Previously, only people with developer accounts on the Marketplace were able to do this. Now anyone with a Windows Phone 7 device, Windows XP SP2 or higher, and a USB cable connecting the phone to a PC can do it.

According to the men behind the software, the idea is to help developers install “experimental”, or “homebrew” applications that would never be published on the Marketplace, such as software that makes use of private or native APIs (application programming interfaces), further encouraging development on the platform. The creators of ChevronWP7 claim they do not condone piracy and that their application is not an enabler for piracy. The jailbreaking of a device using this tool is also completely reversible, they say.

We reported previously that Windows Phone 7 is picking up interest from developers, as Microsoft announced there are 15,000 developers creating apps for the OS. In a way, the release of a jailbreak tool also testifies to an interest in the operating system. Jailbreaking operating systems became popular with Apple‘s iPhone OS and is still a major activity among hackers, keeping up with the release of new versions of the software: Apple’s iOS 4 was jailbroken within hours after its June 21 launch this year.

And interest is something that Microsoft sorely needs. Right now, there are only about 3,000 apps available for Windows Phone 7, but the number should be on a pretty steep rise, as the operating system is just beginning to pick up steam. Still, compare that with Apple’s 300,000 applications available in the App Store and roughly 100,000 apps available for Android devices, and you’ll see Microsoft has its work cut out for it.

The ChevronWP7 tool was first reported by engadget.