Most legitimate developers will provide the source code or an update for a fee.
Years ago, MetaTrader 4 underwent a massive update (Build 600+). Before this update, EX4 files were relatively easy to crack. The refers to an era where decompilers were highly effective. However, modern versions of MT4 use much stronger encryption and a different file structure, making these old "432" links largely obsolete for any EA or indicator created in the last several years. Why People Search for These Links ex4 to mq4 decompiler 40432 link
Decompiling someone else's code can be considered unethical and may violate software licensing agreements. Most legitimate developers will provide the source code