HackMD is the origin of this project, which was mostly developed by Max Wu and Yukai Huang. Originally, this was open source under MIT license, but was relicensed in October 2017 to be AGPLv3. At the same time, hackmd.io was founded to offer a commercial version of HackMD.
The AGPLv3-version was developed and released by the community, this was for a while referred to as "HackMD community edition".
For more on the splitting of the projects, please refer to A note to our community (2017-10-11).
In June 2018, CodiMD was renamed from its former name "HackMD" and continued to be developed under AGPLv3 by the community. We decided to change the name to break the confusion between HackMD (enterprise offering) and CodiMD (community project), as people mistook it for an open core development model.
For the whole renaming story, see the issue where the renaming was discussed.
In March 2019, a discussion over licensing, governance and the future of CodiMD lead to the formation of a distinct GitHub organization. Up to that point, the community project resided in the organization of hackmdio but was for the most part self-organized.
During that debate, we did not reach an agreement that would have allowed us to move the repository, so we simply forked it. We still welcome the HackMD team as part of our community, especially since a large portion of this code base originated with them.