These instructions will help you easily get GRASS installed on VL using slacky.eu repo.
First, enable the slacky.eu repository in Gslapt (about 4th from bottom) so dependencies will be checked automatically, and update your source lists.
Next, install GRASS (Gslapt may complain about an unmet dependency [python 2.5.2] but it should already be installed, just VL-specific rather than slack-specific)
Last, when you're done always make sure your Gslapt has only the 4 basic VL repos selected before exiting (packages, patches, extra, gsb).
That seems to work, however no menu item shows up. You can create one manually or just start 'grass62' from the teminal.