From the author:
MapTrek is an open source software
MapTrek is developed as a hobby for personal use but is generously shared to public on as-is basis. Developers are welcome to contribute to the project. Specifically experts in OpenGL and PostGIS are much needed.
The development is managed on GitHub, there you can find the source code and the list of open issues
If you don’t use any propietary lib or Play Services or things like that it could be added…
Requests for application inclusion should be made on GitLab, so better open a report there:
I am not the developer, but i thought that it could be an interesting opensource app to have available in the repository.
However, I tried to install the apk in 2 devices with Android 4.1.2 Jelly Bean and the installation process failed, so maybe this software is requires a more recent OS or just it is not ready…