Web giant Google, which is backing an assault on the mobile space through its Android initiative, upped the game for open mobile development this week with an unlocked release of the world’s first Android handset.

Targeted at developers, the Android Dev Phone 1, which is sold to consumers as the G1, is a SIM unlocked and hardware unlocked device.

Unlike the operating platform’s bootloader on retail devices, the bootloader on the Dev Phone 1 does not enforce signed system images, which means developers can flash the phone with custom builds of the Android OS. The developer unit also has a funky image printed on the back.

To purchase a Dev Phone, users have to register as an Android developer on the Android Market site, and there is a limit of one device per developer account.

The device itself costs $399, and is initially available for purchase in 18 international markets, including the US, UK, Germany, Japan, India, Canada, France, Taiwan, Spain, Australia, Singapore, Switzerland, Netherlands, Austria, Sweden, Finland, Poland, and Hungary.

Because the device is intended for developers, Google will not offer consumer support. “End users operate these devices at their own risk,” the company said.

Last month, Taiwanese handset manufacturer HTC (High Tech Computer), which makes the G1, said that by the end of 2008 it now expects to shift 1 million units of the G1, available on T-Mobile networks in the US and Europe. This is up from earlier projections of 600,000.