It is supported by the 1992 and 2003 General Conference Resolutions, which provided the basis or understanding that there was a need for programs like this one.
Membership is an ongoing thing, and other countries are notified when a country joins. They may sign treaties for safe nuclear use, but this is not required for initial joining. Since there is no "completion" of the program, there is no certificate.
This program aims to aid the member states in preparing, testing, and improving emergency response for nuclear emergencies and radiological accidents.
The program is targeted for the entire world. They want to advance science while encouraging peace and furthering the training and knowledge of those who will save lives in the face of disaster. This is able to apply to the whole world, based on the possible size of disasters associated with the magnitude of these types of power. Thus, the goal is for everyone to be involved, and most of the world is involved at this point.
Membership is contingent on each state depositing "the necessary legal instruments", and events are held in many different member states, to make educatiuon available all across the world. Those member states control the direction of the agency based on their needs and funding, so it is really self-run to a large degree. Correction to founding question: The IAEA was founded much earlier, in the 1950's to advance knowledge, safety, and peace associated with atomic and nuclear energy. The majority of the world is now involved.
It is funded through member states' voluntary contributions, and in cases where additional funding is needed, they look for money in other areas or from other contributions.
It is an international program with the following member states/countries and the year that they joined:
"1957: Afghanistan, Albania, Argentina, Australia, Austria, Belarus, Brazil, Bulgaria, Canada, Cuba, Denmark, Dominican Republic, Egypt, El Salvador, Ethiopia, France, Germany, Greece, Guatemala, Haiti, Holy See, Hungary, Iceland, India, Indonesia, Israel, Italy, Japan, Republic of Korea, Monaco, Morocco, Myanmar, Netherlands, New Zealand, Norway, Pakistan, Paraguay, Peru, Poland, Portugal, Romania, Russian Federation, Socialist Federal Rep. of Yugoslavia, South Africa, Spain, Sri Lanka, Sweden, Switzerland, Thailand, Tunisia, Turkey, Ukraine, United Kingdom, United States, Venezuela, Viet Nam
Events on the calendar are located in a number of different countries from the above list. The headquarters is in Vienna, Austria.
They have been criticized for slow response to the Fukushima disaster, and by having an official stance as "pro-nuclear energy/usage" they are prone to protests by groups that oppose those views. Some criticism also comes from the fact that member states are not required to follow all nuclear safety guidelines.