From Peter DiCamillo:
Tn3270 is a terminal emulation program for connecting to computers which use IBM 3270 terminals. Major features of the emulation include color, extended highlighting, support for different screen and font sizes, and SSL support. Some more obscure features include support for the APL character set, and support for file transfer and remote printing when tn3270 is used with an IBM VM/CMS host. The Classic version of tn3270 also supports 3179 graphics emulation.
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.