I've cc-ed the ctemplate Google Groups list, which is where current
discussion of ctemlpate takes place. There's not much discussion
though. And there's definitely nothing so formal as to "join" the
project! If there's something you'd like to do with it, feel free to
go ahead. If you come up with something interesting, feel free to
post it to the Google Groups list, or add a patch on the Issues page
at code.google.com, or whatever else might be appropriate.
Have fun,
craig