GuiXT background knowledge:  We wonder what background is necessary for someone who implements GuiXT scripts. Which programming languages is GuiXT scripting similar to?

GuiXT scripts are primarily a notation for screen layout changes and for user actions, with only rudimentary programming language elements. The syntax and functions are quite easy to adopt.

Concerning the required knowledge: you need to know the SAP transaction and  what the users are actually doing. Any programming background will help if you need ABAP functions or want to implement additional features in VB.NET or VBScript. A good screen design requires both a feeling for the visual appearance of the screen and knowledge and ideas about working efficiently with actual SAP business functions.