There are a wide variety of NoSQL technologies. Many of them are schema-less in that they do not require any sort of static schema definition; however, for some of the NoSQL technologies, including some of the schema-less ones, there is still a need for a tool such as Liquibase. Consider MongoDB for example. There is no fixed schema. And in fact, the database and collection (analog to table in RDBMS) does not even get created until you insert data. But for most applications, documents in a collection will have similar structure. The schema just happens to be defined in application code. As with a lot of databases, there is often a need for reference data that is often created and managed with a tool such as Liquibase. So for even something like MongoDB which has no fixed schema, I could see reference data as a possible use case for Liquibase.
Other NoSQL technologies, like Cassandra, are not schema-less. Cassandra is a column oriented key/value store. You do have to define tables (i.e., column families up front). Declaring the columns in a table is optional; however, even if columns are not defined up front, they must all be of the same type. Liquibase is absolutely applicable to Cassandra in large part because Cassandra provides CQL and there is a JDBC driver for it. I have already begun working on Liquibase extensions for Cassandra. I ran into some problems with lock table that Liquibase uses. See this thread for more details. In short, Liquibase’s locking needs to be turned off in order to get things working for Cassandra. I have already submitted a pull request for these changes.