Membership of aSCSa is free. In fact membership is automatic for anyone who attends an ASSC (Australian Systems Safety Conference).
Unless you decide to opt out of automatic membership, then aSCSa will keep your email address for the purposes of privately notifying you of one or more of the following:
upcoming events relating to systems safety (such as the Australian System Safety Conference),
training courses (such as those provided by aSCSa in conjunction with the Australian National or Griffith Universities),
special lectures that may occur from time to time (especially if being provided by a well-known systems safety entity),
availability of the latest, free aSCSa newsletter which you can then download from this website at your leisure.
It is very unlikely that you will receive more than one or two such notifications per month.