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ContributorGuidelines.md

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+# What to contribute
+
+MicroPython is named "Micro" for a reason. We don't want to compete with CPython or replace it. We could spend year of development and do everything what CPython can do, just in 50% of size. It's not worthy an aim. If you want all CPython functionality, you can use CPython right now. What we try to achieve with MicroPython is being order(s) of magnitude smaller than CPython, to use Python (the language) where CPython could not be used at all. This necessitates being a CPython subset, making compromises for what can go into MicroPython core, and then stay orthodox about these compromises.
+
+# Where to contribute
+
+We write MicroPython in C not to keep writing code in C. We write it to let us and everyone write code in Python. This should be good rule of thumb - anything which can be written in Python, should be written in Python, unless there're *really* good reasons to write it in C. 
+
+So, while we cannot achieve full CPython compatibility in MicroPython, we want to have as complete as possible, CPython-compatible standard library written in Python, there's a separate project for that: https://github.com/micropython/micropython-lib .
+
+But note that even micropython-lib has its pretty well defined scope: it's for Python standard library modules, plus, as an exception, to modules we consider to be part of "standard MicroPython library". micropython-lib is not intended to become single destination (or outright dump) of all modules MicroPython. Instead, we would like to achieve the same model as used by Python in general: there's a community, with multitude of modules maintained by individual members of it.
+
+Summing up, you have 3 choices where to contribute with MicroPython development:
+
+* MicroPython core
+* micropython-lib
+* Maintain your own module or port, as part of general MicroPython community  
+
+# How to contribute