I got a new Cisco T1 router with enough flash memory to run an IOS version that supports IPv6. I reconfigured my network a tad and now the Cisco does the freenet tunnel and passes traffic for the rest of the machines.
jcs@hypotenuse:~> telnet -6 dls-gw Trying 3ffe:bc0:932::1... Connected to dls-gw. Escape character is '^]'. User Access Verification Password: dls-gw>sh ver Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(5c), RELEASE SOFTWARE (fc2) Copyright (c) 1986-2004 by cisco Systems, Inc. Compiled Wed 14-Apr-04 04:35 by cmong Image text-base: 0x030802EC, data-base: 0x00001000 ROM: System Bootstrap, Version 11.0(10c)XB2, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1) BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c)XB2, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1) dls-gw uptime is 1 day, 6 hours, 34 minutes System returned to ROM by power-on System image file is "flash:c2500-is-l.123-5c.bin" [...]
Apparently the neteng group at DLS is supposed to start working on IPv6 soon. Hopefully I can get native IPv6 routed here and rt.fm can support it as well.