To replicate build an arma - ar(1,7) ma(1,7) (those are specific lags). From the model estimation screen click Edit->modify model. In the resulting screen the "AR specific lags" box shows lags 1 7 where the "MA specific lags" box is empty (it should contain the lags 1 7).
Gretl version 1.9.1 - windows
---------
Cvet
Thanks for the report. Now fixed in CVS.