I'd surmise that the developer has a new customer or jon that prohibits publication of these applications. It's tempting to wonder if Yahoo/Flickr itself has hired him or her to take the client to the next level, but that's pure guesswork.
In summary, if you have this installed, carry on using and enjoying it. In the meantime, there's always Flickr Central, which I rated as almost as good in my recent review:
Flickr Central is clearly fully featured, but the occasional blind alley in the workflow, together with occasional lag and unexplained pauses (for example, try backing out of the app and then tapping to go back into it again!!) do reinforce the impression that the application is in need of a little attention from the developer for 2015. Hopefully it'll get it.
Can you shed any light on Flickr Booth's disappearance?