I'm not sure that revocability of free software licences really is a problem. However, if it is, this might help:
Free software authors and contributors could sell distribution rights for their work with a contract something like the following. |> Contract made between <name of free software author>, "the |> Licensor", and <name of someone else>, "the Licensee" |> |> The Licensor grants the Licensee a perpetual, non-exclusive |> licence to enjoy all the rights granted in the public licence |> associated with every released version of each Work listed below, |> including the right to sublicence under the same terms. |> |> In consideration of this the Licensee pays the Licensor the sum of |> <one shilling/euro/whatever>. |> |> Works |> |> <list of programs> |> |> Signed |> |> <signature> <signature> People could swap signed slips of paper like that at conferences, etc. If an author ever has their "intellectual property" confiscated there should be plenty of people who are licensed to continue distributing and whose licences remain valid even under Australian law. That's the idea, anyway. Of course, it might be totally broken. On the other hand, just reading that contract and trying to imagine that it might make a difference makes it harder for me to believe that free software licences such as the GPL would otherwise be revocable.