Although a free account is limited to fifteen points a day (bigger textures cost more points), and the biggest sizes are limited to paid accounts, you can get most textures for free at sizes around 1000x1000.
Although most works can use textures for both personal and commercial use freely, textures obviously cannot be redistributed, which means that one cannot share their 3d models with the textures on them as that could lead to a person transferring them on their own work.
The creator does not want users to simply sell or redistribute the textures. However, the licencing is very permissive, and users can share creations that use the textures, such as 3d models.