The 64 bit version of XYplorer is written in the twinBASIC programming language (actually an import of the VB6 source code and forms).
An alternative is B4J, a free (as in beer) BASIC that compiles to Java, so should run just about anywhere. It also has
* B4A - a free version for Android * B4R - a free version for Arduino and ESP8266 * B4I - a paid version for iOS
The main (sole?) developer is ridiculously responsive and helpful.
It seems that can buy a perpetual license for GBP £5000 / developer, which is equal to 16 years of monthly subscription (quite optimistic for a 3yo project).