Thanks for sharing your further plans.
This is to let you know that next generation GroupDocs.Annotation for .NET 3.0.0 is in the release verification process and it may take a week or so to get it released. Like GroupDocs.Viewer for .NET 3.0.0, GroupDocs.Annotation for .NET 3.0.0 will also be a UI-less backend document processing API. In fact, all GroupDocs APIs starting version 3.0.0 will be UI-Agnostic and the related front ends will be open sourced so the users can contribute and fix any issues without waiting anyone. In summary, there are following advantages of this approach:
1) Our product teams will be focused only on back end document processing engine APIs so it is made stronger and stronger to deal with various document formats.
2) The front ends will be disintegrated from the back end document processing engine APIs and will be made open source. This will allow any developer(s) to contribute / fix any front end issues themselves instantly and over the time, front end will be much more improved.
3) Although the front ends will be open source, the GroupDocs Support Teams will keep maintaining and improving them. The public developer(s) will also be encouraged to contribute to improve the front end as mentioned in Point 2 above. This will ensure that front ends are also stable and in working condition all the time.
I hope I have clarified our plans and the respective advantages. In case of any further questions, please do let us know.