this is a free fan game that was made from the ground up using original code. It's not pirating.
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But the point of easyrpg is take rpgmaker2003 games that would run only on windows, and be able to run it on other platforms, i.e. android and mac.
You could say that the games made in this engine are multi-platform by default, being that the support to play on other systems using easyrpg is official, and encouraged by developers.