This site is about recreating gaming and computing hardware from the past in modern programmable devices, known as FPGAs. An FPGA contains an very large array of logic which can be configured by the user to perform just about any imaginable logic function.
They save all the hassle of making your own custom IC, and are a lot less time consuming than wiring up 100,000s of standard logic parts. In modern devices we can fit complete systems, including processors, and they are cheap enough to allow mass production.
It’s not emulation, it’s recreation…. and it’s open source.