Update CONTRIBUTING.md with mention of clean room design

CONTRIBUTING.md

@@ -1,12 +1,32 @@
+# Important
+Anyone wanting to contribute *MUST* read the following and adhere to the steps
+outlined, in order to not violate any Copyright.
+
+This decompile is a [clean room design](https://en.wikipedia.org/wiki/Clean_room_design).
+It *MUST* not incorperate any code owned by Nintendo or other third parties.
+
+In Order to achieve this all code has to be written completely fresh, without
+reference to any third party code, no matter if leaked or not.
+
+Derived from this there is the following requirement for contributors:
+
+- Contributors *MUST NOT* study or refer to any code owned by Nintendo or other
+  third parties.
+
 # Decompiling
 
-These are the rough steps to decompile a function:
+Before starting any decompilation, make sure the project builds correctly:
 
-1. pick a function to decompile (from `asm/`)
-2. make sure it's not one of the few hand-written functions that can't be decompiled
+```
+$ make check
+```
+
+Then these are the rough steps to decompile a function:
+
+1. pick a function to decompile (from `asm/disasm_*.s`)
+2. create a new file in `src/` if necessary (also adjust `linker.ld`)
 3. go through it, roughly line by line, and translate it into C (into the proper file in `src/`)
-4. adjust `linker.ld` if required
-5. compile it, see what doesn't match, and change it
-6. repeat step 4. until everything matches (`make diff` can be helpful, as well as https://cexplore.karathan.at/ and https://decomp.me/)
-7. make sure everything still works (`make check` should give you OK)
-8. open a PR on github
+4. compile it, see what doesn't match, and change it
+5. repeat step 4. until everything matches (`make diff` can be helpful, as well as https://cexplore.karathan.at/ and https://decomp.me/)
+6. make sure everything still works (`make check` should give you OK)
+7. open a PR on github