There is no license fee for either commercial or non-commercial use of the tn3270 application. The tn3270 source code is freely-licensed for non-commercial use, but must be licensed for commercial use.
What's new in this version:
Version 3.4.0 is an update to version 3.3 that supports OS X Mavericks. It also includes experiment support for the tn3270e protocol and for client SSL certificates.