It isn't quite possible. However, there's a number of people that would say the opposite.
From my experience, FreeTDS driver is unreliable and cannot be used in mission-critical production, or even in any production at all. You see, FreeTDS is originally a Sybase driver.
Sybase and Microsoft SQL server have common origins, but it was long, long ago (they split in 1996). Unfortunately, FreeTDS hasn't change since then, but the MSSQL API has, and changes are enormous. So, from my experience, simple SQL queries would probably work, but when it comes to complicated SQL queries or to the stored procedures calls, you will receive errors.
Since 2013 Microsoft has released a native Linux ODBC driver, but they are known to disgust the non Windows enviromnents, so it's version is still 1.0, afaik. But it's worth to try.
I recommend you avoiding wasting time on FreeTDS. Personally, I've seen a couple of PHP and Perl application connecting to modern SQL Server versions and working successfully, but first - you never know; and second - I prefer to take these as some kind of random luck.
You are warned, but you could always try yourself.