Java by Petr Sladek
Telnetd seems to be a complete solution and pretty well documented:
JCTerm behaves like a VT100 and uses a SSH2 connection. But the website indicates the VT100 emulation is incomplete.
JediTerm is the embedded terminal in IntelliJ IDEA. It has both graphical implementation as well as API to override. Graphical version works for remote connections(using JSch) and local pty (using JPty).