Anyone can develop a D&D app based on the 5e Basic Rules. The d20 Fight Club 5e app is a good example (
https://www.facebook.com/pages/d20-Fight-Club/241147409230126). You don't have to deal with WotC copyright unless it's specific content taken from the books that aren't in the Basic Rules. That said, I agree with many folks here and wish WotC would stop sending so many "cease and desist" letters for those trying to create new and interesting applications based off of D&D 5e.
That said, the biggest problem I've seen with most of the apps I've evaluated is that they feel sloppy and not well thought out.
For instance, I want a solid virtual tabletop application that's simple and easy to use and works on my iPad for player viewing. All I want is to be able to load a custom map from a jpeg, add some tokens, be able to zoom easily, and have a simple "fog-of-war" feature where I can hide areas of the map and reveal them as needed.
About the only app I feel I can use right now is MapTool (
http://www.rptools.net/?page=maptool) which doesn't even work on an iPad. As functional as it is though, it still feels clunky so I'm still holding out for a better app.
The one that impresses me the most is 3D Virtual Tabletop (
http://www.3dvirtualtabletop.com). It's simple, easy to use, looks and feels pretty nice, and does most of what I want. I was quite impressed with how it handles the importing of custom maps. The grid alignment tools were probably the easiest I've used out of all the apps I've tried. But the thing that keeps me from using it is the fact that it doesn't have "fog of war". I can't use an app that doesn't allow me to hide areas of the map that I don't want players to see yet.
So, yeah, we have two problems right now:
1. WotC getting in the way of allowing great applications to be created for D&D 5e
2. Lack of quality and focus in the applications being designed and developed
Nothing we can do about the last one except push those designing and developing apps to really pay attention and put the user experience first in the apps they design.
As for WotC, I would recommend that they just create an API that allows folks to pull in content from the API and build killer apps based on the 5e rules and content and be done with it. As the content for D&D 5e grows and rules change, a good API can accommodate those changes and the apps that use it.