In addition to gretl, regarding economic modelling you may also consider Gekko (also GNU GPL licence). It solves large macroeconomic models, such as for instance the ADAM model used by Danish government agencies for macroeconomic forecasting and planning (ADAM has around 3600 equations). It is also used by the University of Copenhagen for a course on macroeconomic planning. Among other things, Gekko has Gauss-Seidel and Newton solvers, equation browser, graphics, tabelling system, Excel integration, help system and installer. It is written in C#.NET, so it is intended for Windows users (it will run under virtualization software though, has been tested ok with for instance Parallels on a Mac).
Gekko has a command language, with commands for handling and updating timeseries etc. The Gekko command language is simple and easier to learn than for instance R (= strongly functional language). I really like R, and I've tried solving a model like the aforementioned ADAM model in R, but the R Newton solver did not seem too comfortable with this kind of problem.
I am the primary developer of Gekko, so my opinions may be biased. Gekko is not Troll or EViews, but it has been used by government agencies since 2008, and it is free.