Windows Based Scripting Host (WSH) is a API to run Active Scripting languages like JScript or VBScript.
If the .js file you're trying to open is from a Windows system originally, it might actually be a JScript file (MS's dialect of JavaScript, or if new enough, a "JScript .NET" file) instead of a regular JavaScript file and have calls to ActiveX, etc.
You might want to take a look at / edit it in the Terminal (with nano for example) first, instead of trying to open it with gedit - just to see what it really contains.
Without knowing more about your system, it is hard to say what process opens when you doubleclick the file - there are several possibilities that can be used to handle .js files, like NodeJS or Rhino, etc. Neither of those are installed by default on Ubuntu, though.