Usage is permitted, as long as:
the [end-]customer is prohibited, either contractually or technically, from
defining, redefining, or modifying the database schema or other
structural aspects of database objects, such as through use of the
Timescale Data Definition Interfaces, in a Timescale Database utilized by
such Value Added Products or Services.
And in fact we already have thousands of companies building commercial applications on top of Timescale Licensed software (while adhering to the license).