This is the RunUO GDK I was making way back in the day. It was faster, better and easier to use in every way over any other tool available at the time. I spent a lot of time on the GDI rendering of gumps so that it doesn't slow down when you add 100+ items to a gump... I was very proud of that haha. I've posted the source code for historical reference only. I'm not maintaining this, nor does it work completely. If someone wants to fork it and finish it, by all means.
For reference I posted screenshots here https://www.servuo.com/threads/nastalgia.2983/