Hello Jeremy,
The Linux version allows you to export VDBs, and people use this option.
However, it's the atmosphere and overall cloud placement inside Terragen that does give very natural results.
Many times that we have seem people export various clouds, it does end up (sometimes) looking like a box of cotton balls. They often look 'placed' and un-natural.
Let me know if you'd like a bit of guidance in this area.
cheers,
Cris.