Ah Ok. I understand.
Yes, unless it’s a public plugin, a private plugin is essentially considered as doing it yourself. AutoChimp needs to have code added to it to tell it how to integrate custom fields from other plugins and third party code. For example, AutoChimp already supports BuddyPress and Register Plus Redux. To integrate those, we had to study the code for those plugins and instruct AutoChimp how, where, and when to access those custom fields. There are several other plugins that are currently not supported. Many people have inquired about other plugins and we’re currently looking into ways to funding a project like that.
You might consider porting your custom fields over to a public plugin like Register Plus Redux. That way, you’d be able to take advantage of AutoChimp. If you use an unsupported public plugin like CIMY, we’ll hopefully be able to support that soon.
Hope this helps!