MSSQL Express 2017 completely free?

i will make a web site with mssql express 2017 on linux.

can i use mssql express 2017?

my web site is commercial web site.

web service will connect mssql express 2017.

i want to install mssql on linux and make web service.

This is for a new Linux server, running MSSQL Express 2017.