Pur autre vie is:

Pur autre vie is a legal term that refers to a specific type of life estate that is measured by the life of someone other than the life tenant. When a life estate is granted to a person (the life tenant) based on the life of another individual, it is considered a life estate "pur autre vie."

This concept also falls under the category of freehold estates, as freehold estates are ownership interests in real property that last for an indefinite duration. A life estate is one type of freehold estate, distinguished by the fact that it lasts only for the duration of a specified person's life.

Thus, the assertion that pur autre vie is both a type of freehold estate and is based on the life of another individual captures its dual nature.