We'd like to announce a new release of jackctlmmc, a command line tool for driving JACK transport using Midi Machine Code that you can download here:
or get the code here:

The program is still in its infancy but it should work for most MMC devices. It currently supports the following MMC commands:
Play / Deferred Play - start transport
Stop - stop transport
Rewind - go to time 0
Goto: go to the specified SMPTE time

It's a pretty simple command line utility for now, but we'll be working on a QT front end soon. To use jackctlmmc:
1) start the program on the command line: ./jackctlmmc -f <your device's SMPTE frame rate> -t <jitter tolerance in milliseconds>
You can also specify -v if you want it to output messages in the console for all MMC commands it's handling, which is useful for testing.
2) connect your midi port to jackctlmmc using either aconnect or JACK's connect (you will have to specify JACK's midi driver as "seq" if you want to connect using JACK).

For the goto command to work, jackctlmmc needs to know your device frame rate which you can specify with -f, or use the default 30 fps. Some MMC devices (like my BR900CD 8-track) are awfully spammy with their goto messages, so we've implemented a jitter tolerance (specified in milliseconds on the command line with -t, defaulting to 50) so jackctlmmc will ignore goto commands that are already close enough to the current JACK transport time.

There's still a lot of work to do on the application, but we've been getting emails asking for progress updates, so we decided to do a quick release now. Hopefully it's useful to people other than ourselves.

-- Alex