Decompiling Maps
Decompiling is the process of taking a compiled level and generating a source that can be opened in a map editor. Decompiled levels mimic the original source, they are not exact reproductions. This makes them useful for learning, measurement, and inspection, but not direct recompilation. The original source is ideal for reproductions or modifications.
Releasing reproductions, modifications, or approximations of another's work without permission is breaking copyright law.
Tools
Getting dirty
The latest decompiler is called BSPSource and is written in Java. You need an updated version of the Java Runtime Environment (JRE), which can be downloaded from Sun to run BSPSource. Once installed, you are ready to decompile your first map.
See Also
Before you go
Before you take this jump to run off and decompile a map take a second or two to think, "What am I trying to learn/do?". Read the included TXT files, you may just find the creator's e-mail, and that could be more helpful than you imagine.
Some mappers will offer up help and advice, they may even go so far as to provide perfect examples of what you were trying to "borrow" from the map.