The people who decided to make it stopped. 

There have been efforts since, but mostly the devs have gone dark.

I know it's not the same thing, but you could use the current Dragon Language Dictionary PDF:  Click here for the PDF! 

Go to the library and you will find it as the forth item down if you don't want a direct download.  Click here for the library!

It's a useful resource and I utilize its features often when writing Dovahzul songs and poems, even in full canon. The app is outdated and the Legacy words are from way too long ago for most of them to be at all useful, but the app itself is helpful. I'd like to see it remade for the canon dictionary, with all the same features.

I haven't checked the Google Play store for a while, so I don't know if the app is still available on there or not, but I know for a fact that it's not available on the Apple store.