Membership of the Open Source Specialist Group (OSSG) is through the BCS. You can find out about membership on the main BCS website. All members are notified of upcoming events by email and are entitled to vote in Open Source Specialist Group elections.
However all our events are open to non-members. Most meetings are free, although a small fee may be charged for entry to certain events. The great majority of our events are held jointly with the UK Open Source Hardware User Group (OSHUG), who run their own mailing list notifying about events.