Does anyone else think this should be on blackberry's and other phones not just android ones? I think it would 1)Boost the popularity and 2) increase the linguistic skills of many people.
There's also an app for iPhone.
While I agree it would be great to make Duolingo available to more and more people, the two apps available now cover 93% of smartphone users around the world (http://tinylink.in/5E1K) so I wouldn't count on seeing apps for Blackberry (3%) or Windows Phone (4%) any time soon. You never know, though!
As ever, it's a question of how Duolingo should best allocate its limited resources. Developing a good native app takes a lot of time and effort, and the currently available apps serve around 93% of all smartphone owners worldwide -- that's really not too bad! In particular, given the current state of Blackberry, it would be a very risky bet to start devoting resources to a Blackberry port. As for windows: if Windows Phone ever gets significantly beyond the current market share (around 3%) it might be worth developing for, but that's not going to happen for a while, if ever. Microsoft's previous forays into the mobile world haven't ended well (see e.g. Windows Mobile).
It's currently an interesting time for the mobile OS world, with Sailfish, Tizen, Ubuntu, and Firefox all scrambling for a piece of the pie (and probably some others that I haven't heard about). There's no way to tell who will be left standing in a couple of years' time, so it's a risky gamble to start developing for niche OSs at present.
Of course I'm not privy to Duolingo's plans, but this is how I would look at the situation if I were considering the development of further mobile apps.