See Sympa SOAP server.
See Sympa's RSS channel.
You may extract subscribers, owners and editors for a list from any of:
See the user_data_source list parameter.
The three tables can have more fields than the one used by Sympa, by defining these additional fields, they will be available from within Sympa's authorization scenarios and templates (see db_additional_subscriber_fields and db_additional_user_fields).
See Data inclusion file.
The number of subscribers of a list can be obtained from an external application by requesting function
subscriber_count on the Web interface.