To try Wordfast before you buy, please just download the software and test it out for as long as you like, there is no time limit. There are 2 limitations on the software without a purchased license. You will not be able to connect to a Remote TM and your Local TM will be restricted to 500 TU's.
When you are ready to purchase your Wordfast Translation Studio license which is valid for 3 years, you can visit www.wordfast.com and click the "Buy" button. If you have any questions regarding purchasing your license please email firstname.lastname@example.org . Once you purchase the license, you will receive an email with a user name and password. You can then login to the support system and license your applications.