Oxygen Viewer is a model / island viewing tool.
BIS calls it Oxygen Viewer, community calls it Buldozer instead. It is the 3d viewer to show the model open in O2, you can move/rotate the model freely in this view. It also displays the island loaded in Visitor 2 in real time when making edits.
Download o2_viewer.zip from BIS page.
How to run Buldozer viewer without OFP being installed?
From your OFP installation export the Reg Key from your Registry. Keep the Reg file for future use, make a backup of the reg file in a .RAR archive. That way you can use it if you ever need it again without installing the game.
If you have the Reg file you simple double click it. It's gonna ask “Are you sure you want to add the information in C:\X\X\X\Reg_File.reg to the registry?” just click yes and it's like you installed the game.