The attachemnt description field in gas was provisioned for future release. If you have installed GAS 3.x than you will already have an description field in your attachment table. I hadnt yet put the UI in place for it (and now I dont!

). I pushed it into the first 3.0 release so I could import v3articles and keep their descrptions.
This hack should be totally compatible. You may get an error doing an alter table as the column already exists - but everything else should slot in nicely.
Good job - it is a seriously missing element of vB