The best free alternative to Nucleus is RPCS3, which is also Open Source. If that doesn't suit you, our users have ranked four alternatives to Nucleus and four of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to Nucleus are ChonkyStation3, aPS3e and Short Waves.
RPCS3 is an experimental open-source Sony PlayStation 3 emulator and debugger written in C++ for Windows, Mac and Linux. RPCS3 began development in May of 2011 by its founders, DH and Hykem.
aPS3e is an Android-based PS3 emulator built from the RPCS3 source code, adhering to the GPLv2 license.
Short Waves is a PS3 emulator for windows. (Very early release, can run a few homebrews)
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