We use the same policies as the Asset Store and we publish assets in 3 Categories (Tools, Templates and 3D). The Asset Store defines several license types depending on which category the asset is placed in. Here is a simple overview of the current license requirements in order to remain legal, as well as a link to their license FAQ. You can easily see which license type an asset uses by visiting the Product page on the Asset Store.
If you are a solo dev, don't worry about any of this. Just go have fun - you're legal =)
Per Seat License
If the Asset is in the Tools or Templates category then all users who are working on the project are required to have their own 'seat', or in other words, an additional license.
For example if you have 5 people working on a project but you only own 1 seat of Vault (for example) then your usage is considered illegal and 4 additional seats are required.
Having insufficient seats for your product violates the EULA and invalidates your license rights.
Single Entity or Multi Entity
If the Asset is in the 3D category then you only ever need one license. The options are Single Entity and Multi Entity. The term "entity" is loosely defined as your company, or you personally.
- Single Entity: One license of this type covers your entire company, excluding contractors and other companies.
- Multi Entity: One license of this type covers your entire company, including contractors, and other businesses on the project.