Writing code is the most direct way to contribute this project. Both the source code and issue list are open.
It seems simple, but you need to understand SEGA Saturn hardware well and have skill developing software using C, Android, OpenGL, ARM.
There are many android devices, controllers. To make uoYabause run on these devices, the developer needs to obtain them and debug on them. Sending the device on which you want to run uoYabause to the developer is the most efficient way. If you can't, donating money to developer helps to obtain devices. You can donate the developer using the uoYabause interface. And this paypal button.
SEGA Saturn was sold all around the world and there are people everywhere waiting for this emulator. You can translate android ui editing "yabause\src\android\app\src\main\res\values\strings.xml". For more detail please refer https://developer.android.com/intl/ja/training/basics/supporting-devices/languages.html
Reporting bug is very important to determine what the developer should do. We have two way to report bugs.