The error is telling you that you're not using GumpPlus from Solaris Utilities and instead are using GumpPlus through Knives, which has certain calls that this MotD setup isn't using.
I did, however, find a copy of the original Solaris Utilities - GumpPlus. I DO NOT guarantee if this will even compile, but my suggestions are:
Before installing -
1. Rename all instances of GumpPlus to GumpPlus2 in the GumpPlus folder for Utilities.
2. Now, go into all the MotD scripts and change all instances of GumpPlus to GumpPlus2 and it will use the proper "GumpPlus".
3. Do a save/restart after the server boots and you log in to the world.
4. Setup a new MotD and do some testing.