you can use any Game Boy, Game Boy colour or Game Boy advance emulator to execute the .gb file.
I use Emulicious to test and play the ROM, it uses Java

Controls

D-pad up/down - increase/decrease selected field or change the sign or mathematical operation
D-pad right/left - move cursor

Start - clears selected number
Select - load stored value into selected field

a - starts calculation
b - store the result for later use