Reclamation of vms as others have mentioned and the service limitations as to what qualifies for the free tier are really the only catch, but not a problem if you're willing to give them your credit card info for a paygo acct. More details are in this link to the docs. It's honestly a really good deal and I find it way more transparent and easier to use than AWS.
https://docs.oracle.com/en-us/iaas/Content/FreeTier/freetier_topic-Always_Free_Resources.htm
Reclamation of vms as others have mentioned and the service limitations as to what qualifies for the free tier are really the only catch, but not a problem if you're willing to give them your credit card info for a paygo acct. More details are in this link to the docs. It's honestly a really good deal and I find it way more transparent and easier to use than AWS.