The generator matrix

 1  0  0  1  1  1  X  1  1
 0  1  0  X  1 X+1  1  X  0
 0  0  1  1 X+1  X  1 X+1  1

generates a code of length 9 over Z2[X]/(X^2) who´s minimum homogenous weight is 8.

Homogenous weight enumerator: w(x)=1x^0+45x^8+18x^12

The gray image is a linear code over GF(2) with n=18, k=6 and d=8.
As d=8 is an upper bound for linear (18,6,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 6.
This code was found by Heurico 1.16 in 0.00025 seconds.