An "open" AA meeting is defined best by A.A. General Services in New York (click on the image to enlarge it):

For our meeting purposes, what this means is -- "the only requirement for attending our online meetings is to have a desire to stop drinking." That is all that is required to become a regular member of the group.

Outside of that however, "non-AA visitors" - psychology students for example - are also welcome to attend as observers. Early in each meeting we invite our non-AA visitors to introduce themselves and ask only that they not share during the member-sharing part of our meetings. Those sent to us by the courts are welcome to join us any day as well.

We commonly have new friends come and attend our meetings for a time who have been sent to us (well, more accurately, sent to A.A.) by the courts. We know this can be for any number of reasons - reasons which many of our regular members also have experienced. If you are one of these people, you are of course also welcome to attend our meetings as often as necessary (refer to section above about "open" A.A. meetings).

For those needing proof of attendance at AA meetings, whether sent to us by the judicial system or by the educational system (student observers also commonly need some form of proof they attended a meeting), we do supply an accepted form of verification for whatever number of AA meetings one needs to attend. Please do keep in mind, however, that this is strictly a voluntary public service - that neither Alcoholics Anonymous World Services nor any local or online A.A. group (each group being fully autonomous from each other and from A.A. as a whole) is compelled to, or responsible for, providing this service. Additionally it is the responsibility of the person needing attendance verification to follow our process (meaning they ought  not insist on needing special forms of proof such as daily scanned signatures, etc.) as well as to submit requests for verification in a timely manner, directly after each meeting attended. We verify attendance for those we can physically see in attendance for each full, 1-hour meeting. We do not and cannot rightly verify attendance for partial meetings, late-comers or meetings that took place in the past, weeks or a month ago.