At the end of the page, you will find four files:
java-marketpay-pos-api-21-documentation.zip
Documentation on C# integration
ECR Simulator v21.1.0.0.exe
ECR simulator
ecrsimulator v21.1.0.0.zip
ECR simulator source code, to have code examples for ECR integration
marketpay-pos-api-21.1.0.jar
libraries to proceed with ECR integration
There a library marketpay-driver-cpp.dll which is Core library, written in C++. This file is not needed at build time because it's dynamically linked in runtime. But it has to be reached by .exe program.