Apple's mobile operating system, iOS, continues to remain the apple in the developers' eyes while Microsoft's Windows Phone 7 showed renewed interest among developers, according to the fourth-quarter mobile developer report from Appcelerator and IDC.

The survey says that iOS remains the leading platform of interest with the launch of iOS 5 stealing share from Android. It also showed that 91 percent of respondents saying they are very interested in developing apps for the iPhone, followed by the iPad at 88 percent which was aided by the recent software upgrade to iOS 5.

Interest for the Android phone fell nearly 4 percent quarter-to-quarter to 83 percent while the Android tablet fell nearly 6 percent to 68 percent as interest in iOS 5 and weak Android tablet sales weighed on the Google OS platform.

One of the most significant moves came from a renewed interest in Microsoft's Windows Phone 7 (WP7), which clearly vaulted ahead of RIM's BlackBerry OS to become the No. 3 mobile OS behind iOS and Android, increasing 8 percent quarter-over-quarter, with 38 percent of respondents showing interest in the platform.

The renewed interest in WP7 was aided by the launch of the Nokia Lumia family, the new Windows Phone Mango (7.5) release, and the potential for tablets and Windows 8 integration. In addition, Nokia is seeing resurgence with 28 percent of global developers and businesses interested, which is more than double the level of interest in Symbian or Meego, according to Appcelerator and IDC.

Meanwhile, the interest for the BlackBerry Phone OS dropped sequentially from 28 percent to 21 percent and Blackberry PlayBook from 20 percent to 13 percent.