Both Plug-Ins made by the "Ofnuts" person.
The "Path-Inbetweener" Plug-In creates many layers of Paths within two existing Paths, sectioning your shape up so that it looks like an integration maths problem. Then apparently the "Stroke-Visible-Lines" Plug-In is supposed to be able apply incremental colours from a Gradient to each of those intermediary Paths, so that in theory, with enough intermediary layers, you should be able to apply a colour gradient to a custom shape: by tracing the shape's outline with a Path and then a miniature of the shape at its centre, filling the intermediary space with additional paths, then 'Stroking' those paths with individual increments of a colour-gradient. However all I can achieve using that Plug-In tool is to apply the Background colour to all of those paths.
The "Path-Inbetweener" Plug-In creates many layers of Paths within two existing Paths, sectioning your shape up so that it looks like an integration maths problem. Then apparently the "Stroke-Visible-Lines" Plug-In is supposed to be able apply incremental colours from a Gradient to each of those intermediary Paths, so that in theory, with enough intermediary layers, you should be able to apply a colour gradient to a custom shape: by tracing the shape's outline with a Path and then a miniature of the shape at its centre, filling the intermediary space with additional paths, then 'Stroking' those paths with individual increments of a colour-gradient. However all I can achieve using that Plug-In tool is to apply the Background colour to all of those paths.