The grids are not very hard to makes, unfortunately, I don't write very well in English, thus the readme is hard to understand.
The grid doesn't stay up more than those 10 seconds. That's because if someone inadvertently started gridmove's grid and couldn't close it, it'd close itself.
GridMove protects the user from himself, not moving windows which are not supposed to be moved. Your java program is probably one of these.
However, you can disable this feature in the menu, under 'safe mode'. Be careful though.. If you disable it, GridMove will be able to resize any window (including some which shouldn't be moved!).