As a contributor of 30% of the commits, and the author of many important subsystems in MicroPython, I have my repository at https://github.com/pfalcon/micropython . The fork exists for a year now. Well, it actually exists for 5 years, except during initial 4 years, 95% of changes were going directly to upstream.
The focus of the port is:
- Finishing/making complete subsystem/features started in the upstream
- More complete documentation (at http://pycopy.readthedocs.io/)
- Exploring new "computer science"-level ideas (new for MicroPython, not computer science )
For as long as possible (was possible for a year), the fork is rebased on the upstream. As much as resources allow, I submit changes back to upstream, but my resources for that are limited, and pipe there is narrow.