Charities must meet certain criteria to join the program. For example, in Australia charities would need a Deductible Gift Recipient (DGR) Item 1 and Tax Concession Charity (TCC) status.
You can check to see if a charity has DGR Item 1 by searching here if your charity is in Australia. If you are in New Zealand you will need to ensure you have Donee status.
There is an annual membership fee of AUD 330.00 (inc GST) to register with the GoodCompany Foundation in Australia and NZD 345.00.