Binary Translators (Desktop Software Reimplementations): open-source projects that exist because someone reverse engineered a closed product, sorted by GitHub stars.
Fast usermode x86/x86-64 emulator for ARM64 Linux
Tiny x86-64 Linux emulator that runs on many platforms
Linux userspace x86_64 emulator for ARM64, RISC-V and LoongArch with native lib wrapping
Linux userspace x86 emulator for ARM with native library wrapping
Runs Windows x86 apps in Termux on Android with Box64 and Wine
Runs Win32/Win64 x86 apps on ARM64 and other hosts using Wine with FEX/Box64
Xbox 360 executable to Windows executable static recompiler
x86-64 userspace emulator for RISC-V Linux
Binary to LLVM IR translator
Dynamic binary lifting and recompilation
MIPS to C decompiler for the SGI ElectroPaint program
Native Apple Silicon port of SpaceEngine by static recompilation of the Windows executable