Royalty Free License
The Royalty Free license grants you, the purchaser, the ability to make use of the purchased product for personal, educational, or commercial purposes as long as those purposes do not violate any of the following:
You may not resell, redistribute, or repackage the purchased product without explicit permission from the original author
You may not use the purchased product in a logo, watermark, or trademark of any kind
Exception: shader, material, and texture products are exempt from this rule. These products are much the same as colors, and such are a secondary meaning and may be used as part of a logo, watermark, or trademark.