Hi Patrick ,
We can make non-editable Material Description field in MM02 tcode.
Just follow the steps:
1. Tcode:OMSR find MAKT-MAKTX field
2. click on field selection maintenance button 
beside selection group ''20" for the field MAKT-MAKTX.
3. system shows change view "field selection for data screen"
4. Under field selection select MM02 check display radio button as show in screen shot.
5. Save the data.
6. Now go to MM02 Transaction
give material number selection organization levels
Material description show display mode for all the organization views
Hope it is useful to you
Regards,
B V Yadav,