This is an image, data, and function plotter. Function parameters can be manually tuned [or automatically fitted - not yet implemented] to given xy data. High-level scripting capability is provided [not yet] by the underlying Python programming language.
Descartes is platform independent; it runs under Linux as well as under non-free operating systems.
Descartes is open source software; it is distributed for free, and protected by the GNU public licence.