are there any plans to move it to https://github.com/grails-plugins or https://github.com/gpc ?

I'm reaching out to Peter who was the creator (by mail)

we had also discussed to move that one to the ASF at one point, but I don't think we had the contirbutors to do it. It would make sense to move it to grails-plugins

I think I could tackle the upgrade to Grails 7 with some support

I just had an answer from Peter McNeil:

Yes I have been busy and lax in updating grails plugins. I'll have a look.

Do we have some kind of expected time window for this or could it be worth (and no double effort) to start the port ourselves?

@Peter McNeil what is your time frame on this?