It would be very cool to have this under the right click and then somewhere in Filters list where you could affect more than one Path at once

Well what it does is create an inside or outside selection along with the original correct?Then you are able to fill it or stroke it?

If you stroke it will it stroke two lines (one on each side of the selection value you enter)?

<Vectors>/Parallel path - i suppose would be appropriate as you would be working with Paths at the time.

Am i correct in assuming what the script does?

A picture is worth a thousands words...

Very cool, the picture explains it perfectly, although I am not sure, you mean the gray was original? And assuming from the fact I see the Open path picture there, is the script done?

I look forward to seeing your code (he said in understated tones). Are you implementing Thomas Hein's "Flattening of Cubic Bézier Offset Curves"?

No, I'm using a brute force approach, iterating the strokes, finding the coordinates of the point at requested distance on the perpendicular, and so generating a huge number of lineto() that Gimp seems to handle very well (my code for this is a derivative of my Slinky plugin, for which I doubt there is a nice mathematical solution).

For the simple case we have here, I thought there could be a more subtle solution and your pointer is good news. However the text of the article on various sites is protected by a 30$+ fee and since I'm not expecting any financial compensation on the script I won't bother.

The paper in question, if anyone is interested, below:

Cool. Now grabbing the aspirin...

Looks exactly how i pictured it.
I shall now do double duty rain dancing -

It's basically finished, just needs a bit more testing, and then creation of a SourceForge project. This could happen tonight. On the other hand, on weekdays, available time for pythonic Gimp isn't very weather-dependent (in fact if it rains my motorcycle commuting takes longer). It would be more appropriate to pray Vishnu, Shiva and other gods for painless integration of the code provided by my offshore correspondents, so I can come home early.

(fortunately you have lost your powers, it's very sunny this morning).