Hi Jingwu, Thanks for your interest. Anyone is allowed to join the mailing lists.
The instructions are available on the website: https://calcite.apache.org/community/#mailing-lists
Jingwu Li wrote:
We are doing POC to use calcite and avatica to connect to different backend data stores. I would like to join the community in order to post questions and feedbacks. Regards, Jingwu Li