InnoDB is a standard part of all MariaDB 10.x processes.
InnoDB can be added to older processes (i.e. MariaDB 5.3) that do not already have it. To do so, enable it from the Actions box on the MySQL info panel for that process. (A small additional fee applies.)
InnoDB cannot be completely removed. If you do not want to use it and you have a MariaDB 10.x process, you can attempt to disable it to save money by using a custom configuration similar to:
default-storage-engine = MyISAM
innodb = OFF
This setting may cause your process to use less memory (and therefore cost less), but please make very, very sure you don't have any important data in InnoDB tables before disabling it.
We do strongly recommend using InnoDB whenever possible. We use it ourselves, exclusively. The power and reliability of InnoDB are well worth the small additional cost.