You might be able to talk with the Stacked team about upgrading your plan from your current plan (by paying an extra $10). I think they've done this in the past. By doing this you would not only get the link removed but would also get 3 EasySocial themes instead of one. Plus you help further support an awesome team of enthusiastic web developers who greatly support our web communities.
The Professional plan is the greatest value for your money. So you will have to talk it over with the Stackideas guys (ideally in private) to work out an upgrade. The install package will pretty much be the same. I never had the starter package, so I assume that you just reinstall the launcher and it gets overwritten.
Perhaps If you feel free to drop us an email at support@stackideas.com regarding this. (If you didn't receive any reply from your email, keep us update on this thread.)