The source and some build instructions for the installer can be found here
In changeset [https://github.com/corbinlc/octave4android/tree/6687c0b2826c1ee35496c1679ae756e34fe0d953 6687c0b282], there were 27,904 deletions which makes the repo in 23.Mai 2014 almost empty. You can use the its parent [https://github.com/corbinlc/octave4android/tree/b3bb7f6de607a99840f8b4e6dd40ae12460d2563 b3bb7f6de6] instead. You are offered a choice of downloading the app, for which a donaction is requested, or you can download the full source and build your own version for free. This will require the Octave sources, Corbin's GitHub repository, and the Android SDK.
This implementation has been done in close cooperation with the Octave developers and makes use of the current Octave source essentially without any change. Thus, it is fully compatible with the versions of Octave on other platforms.