If you create a SureSync or SureSync MFT SQL database with Full Recovery mode, the .ldf file will not be truncated until you run a backup. There is no harm in a large .ldf file but it can consume a lot of storage. It is strongly recommended that you perform regular backups of your SureSync database. This will protect the database and keep the .ldf file size in check.
The other option is to use the Simple Recovery mode. In SQL Management Studio, you can find the Recovery Model for the database by right-clicking on the SureSync database and selecting Properties. Click on Options, and there is a Recovery Model drop-down. By default, the SureSync database is created with a Simple Recovery Model. An option to "Auto Shrink" can also be enabled. Simple and Auto Shrink should result in a very small transaction log file.
The default maintenance plan provided with SQL Server should be fine for use with your SureSync database. You can find further documentation on truncating logs in your SQL documentation. Please visit Microsoft's Manage transaction log file size article as a starting point.