Microsoft's current smartphone operating system, Windows Phone 8.1, has lagged the Google Play Store when it comes to applications available from the Windows Market. There are many applications for the platform, but there isn't the sheer volume that we can find on the Play Store. This is despite Microsoft's efforts in encouraging developers to write quality applications and games for the platform. Things are set to improve with the adoption of Windows 10, which will see the introduction of "universal applications," that is, one application written regardless of the detail of the platform from mobile to tablet to laptop to desktop. However, there are persistent concerns that this will not be enough... and similar persistent rumors that Microsoft has been effectively courting their enemy by tinkering with allowing Android applications onto the Windows platform.
Android applications can be found running on other operating systems, with Sailfish OS and BlackBerry 10 being the two most obvious examples. There are often compatibility issues associated with the lack of Google Play Services on a non-Google Android platform. However, putting aside the complexities of running the application, the very idea of introducing Android applications to the Windows 10 environment is a complicated issue. If Microsoft designs Windows with some element of Android application compatibility, this is something of an insult to those Windows developers who have invested time and effort into bringing native applications to the platform. They have been encouraged to develop; if Microsoft open up the Android gates, this may nullify their efforts and could undo a lot of the developer encouragement that Microsoft have been working on for the last four years.
However, there's another reason why Android application compatibility may not make it into the final release version of Windows 10, which is a legal issue. At the time of writing, we do not know the detail as Microsoft is keeping things quiet, but the belief is that it could lead to a lawsuit from Google because of the way Windows 10 may emulate the Android platform. Given how Microsoft has pursued the Android device manufacturers for royalty deals, especially Samsung, perhaps Google would be only too ready to challenge Microsoft? As we understand, despite these issues Microsoft is still considering releasing some form of emulation to allow Windows 10 to run Android applications and as such, is internally developing and experimenting with the idea. We don't know how advanced this development is and Microsoft said that "they have nothing to share" on the matter. However, putting Android applications onto Windows 10 is a tantalizing idea.