At the time when new version of this application was published (March 2016) - there is no direct competitor applications in the segment of muti-platform 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.
* - as of end of March 2016, new version of AGB Oil Calc (PB Edition) available only for Windows OS. For other OS - please use older Java version of AGB Oil Calc application. New version for these operation systems would be available shortly.