Our company policy has always been to support the current version and one version back.
It just takes us a long time to repeat all of our QA on multiple platforms and give our seal of approval. With Adobe adding 5.5 to the mix it has already greatly increased our QA effort so that supporting the current version and one version back now means testing on CS5.5, CS5, and CS4.
I can probably get a build made that I can send you that will install on CS3, but I can't promise that it will work (although I suppose it would) and if you do run into any CS3 related issues we won't be able to solve them since it won't be officially supported.
I opened a support ticket to give you a location where you can download a version that will install on CS3. I'll update the ticket once it is ready. Just a forewarning that any extensions moving forward will not be officially supported on CS3.