If you truly need source code from an EX4 file, here are the ethical and practical paths:
Most free decompilers, like EX4 to MQ4 Decompiler 4.0.432 , only work for MT4 build 509 or lower. Modern EX4 files are heavily protected and will not work with these tools. Free Ex4 To Mq4 Decompiler Software Applications
Free EX4 to MQ4 Decompilers: What They Are, The Risks, and Why You Should Avoid Them If you truly need source code from an
In the early days of MT4, decompilation was relatively simple because the encryption was weak. That changed significantly after like EX4 to MQ4 Decompiler 4.0.432
Most "free" decompilers available online are outdated and struggle with modern MetaTrader builds.