It's a native Android Java application, with at least one very active developer. The license is LGPL. It has very good address/place search capabilities and UI. It has a lot of different functions which can be used while online and I didn't explore them.
However the vector rendering functionality make this program the most promising out of the free android map applications for offline usage out there.
At this stage it's quite difficult to get/prepare your dataset and also there are problems when using bigger datasets. The problems are being worked out and once that happens it's going to be THE application to use when on travels.