Not clear with your question,Can you please rephrase or put it correctly.
I'm intended to generate .TWBX using "TABCMD GET" function and make it automatic by using Batch file and sent the twbx file to users so users can open it with Tableau Reader.
my question is :
1. Is it a normal use? any user license agreement rule any kind of this activity?
Yes you can do that and it will not get any issue with license, but one thing is if the customer have desktop then they can able to see your own data.
You can use batch script and send to other people.
use any command line tool for this.
first get the workbook and then use command line tool to send mail.