GUI Octave

Bad news

The GUI-Octave project seems to have been discontinued. Even if it is still alive it is not (for me) an active enough project to buy in to at the moment.

Python

Looking for a free programming language and development environment? Looking for something a bit like Matlab, that provides command line execution and scripting in addition to program development, and also easy graph plotting? You could do a lot worse than Spyder which is a front end for Python. It is really very impressive - steeper learning curve but worth it.

R

Download R and RStudio (both free). R is long winded but immensely powerful and Matlab users might be pleasantly surprised by how quickly they will pick it up.