I was browsing for free image editors which support layers when I stumbled upon John Paul Chacha's site.
The heading "Kenyan software at its very best" brought a smile to my face although I know that was very patronising of me.
Anyway, the program I looked at was Chasys Draw IES. It doesn't appear on the radar very often. I played with it for a while and was quite impressed. It had an appearance of quality about it.
Unfortunately I suspect that it is not portable - can an expert confirm that?
Also on the site there was a program Chasys Math (v 1.31)
This is a suite of math utilities including a calculator featuring graph-plotting, complex numbers and visually-perfect algebraic method (Chasys Math Calculator), and a matrix equation solver that can handle systems of equations as large as 32 by 32 (Chasys Math Matrix). It is probably portable. The files are obtained by installation/copy/uninstallation.
Find it at ...http://www.jpchacha.com/chasysmath/