At the time when this application was published (April 2015) - there is no direct competitor applications in the segment of Android OS applications designed for the oil and gas reserves computation (in terms of supported computation algorithms, units, methods).
Application source code was created to be multi-platform and at present time this application available for the following platforms: Android OS, Windows OS and Linux OS. Quite possible that there would be a version released for MacOS as well. Most likely distribution conditions for all of they would stay the same - as freeware application license. Release of iOS version also possible - but not planned because it's required significant financial investments - and as a result not currently planned until external investment would be available.