The first google hit (german sort order) took me to a swiss / german language site
Next obvious query is YTD InDesign, which leads you to a product called "Yours Truly Designer" from HP.
Searching the HP site is a pain, apparently they never heard of Search Engine Optimization.
The closest in content pages that I found are press releases announcing YTD for CS2, and a $2640 course for HP Indigo Front End Tools.
Basically you are right, just that scripts are a different category. Plugins can add their own "persistent data" to the document.
To remove the message and all irritating data, export to IDML (or INX if you're using older versions) and rebuild the document from that export.
As this is the place where plugin developers hang out, let's take a mental note to:
- add appropriate "IgnoreTags" resource so the users are not bothered by that dialog.
- maintain a "ExtraPluginInfo" resource with readable ( non localized ) strings
- test without the plugin!
But of course we all knew that