The AO3 is an archive of fanfiction for multiple fandoms, founded and run by a non-profit organization, Organization for Transformative Works with the aim of "providing access to and preserving the history of fanworks and fan culture in its myriad forms."
And, well, there's also the fact that...
"[...] the Archive is one of a very small number of open-source projects founded and largely staffed by women, another contribution fans have made to the internet as a whole. Many women who were not previously involved in technology have learned new skills in the name of fannish activities, and the AO3 is proud to stand as a shining example of this growth."
So, congratulations AO3!