MATLAB for students and home use and individual professionals, and some educational use, is sold as a one time purchase. Except perhaps for students, this provides the right to use any previous version. However, this does not provide rights to any upgrades after the first year.
People who purchase this way can also subscribe to maintenance service which provides upgrades and provides technical support rights (though students do not get technical support if I recall)
Commercial and educational organizations also have the option to pay for limited time licenses, such as for one year, after which the software would stop working. One reason this option is provided is that for accounting purposes this is often considered a Service (operations budget) rather than a Purchase (capital budget). There are even some organizations which have to deal with regulations forbidding them from "purchasing" software. So term licenses are available from Mathworks, but they are not what most people would get.
(I have even run into stories of organizations not permitted to purchase software, but also not permitted to use Open Source software. Because politics: the appropriate oversight committee was being run by politicians who could not close the organization for legal reasons, but could deliberately make it hard to get any useful work done.)
