Hi Sergei, a minor bug with the GetString function. The following code [code]
nucFreqs = [0.2}{0.3}{0.2}{0.3];
global kappa = 1.0;
nucMatrix =      [*, t*kappa, t, t*kappa }                        
                 { t*kappa, *, t*kappa,      t }
                 { t, t*kappa, *, t*kappa }
                 { t*kappa, t, t*kappa, * ];
Model nucModel = ( nucMatrix, nucFreqs, 1 );                              
Tree nucTree = (A,((B,((C,D),(E,F))),((G,H),(I,J))));
GetString ( ModelString, nucModel, -1 );
fprintf ( stdout, ModelString, "\n" );
[/code]

returns  0.26*t+0.48*kappat instead of 0.26*t+0.48*kappa*t. cheers ./w

Dear Wayne,

Fixed in today's build thanks! I plugged in some old polynomial code to do expression simplification, and forgot to undo the old shorthand (i.e. xyz instead of x*y*z).

Cheers,
Sergei