Free for non-commercial use
You're good to go as long as you do not sell or otherwise profit from any work containing the assets you build within World Machine.
If you want to do that, or need higher resolution output, you can buy one of our commercial licenses.
This is not a time limited trial.
The only feature limitation of the free Basic Edition is that you cannot build or output an asset larger than 513x513 pixels.
Otherwise, you have access to everything in the Standard Edition!