I heard that I needed to run two programs to get the IBM WinOS2 TCP/IP support working better.
1. Run \MPTN\BIN\VDOSCTL.EXE
2. Inside WinOS2, run \TCPIP\DOS\BIN\TCPCNTL.EXE
After doing those two things, the Mocha telnet is working. I did not yet try the TN5250 or TN3270, but I'll bet they work fine, too.
The only thing wrong is that on my SMP system, all cores are working at 100%. Does anyone know if there is a DOS Setting that controls programs that hog the CPU by polling?