Technically, decoding is a form of reverse engineering. While ionCube uses advanced obfuscation and dynamic encryption keys to prevent this, the bytecode must eventually be processed by the server, which creates a theoretical window for extraction.
Decoding ionCube-protected files is not a straightforward "unzip" process. Because the source code is converted into bytecode, a decoder must essentially perform "reverse compilation." This involves: ioncube decoder php 74