So it turns out that, as people have been telling me, the MT software license is in fact pretty not-open. Among other things, it says
You may not redistribute the Software without Licensor’s prior
written consent. Although you may modify or create derivative copies
of the Software for your own use, you may not distribute modified or
derivative copies of the Software.
I suppose that’s pretty normal for software, but does not mesh with the way that I view the world, and, I suppose, it’s pretty clear that I’ve already violated it, having distributed modified versions of various parts of the software. So I suppose I’ll have to find some other package to migrate to. I’m leaning towards Ken Coar’s software, if he lets me use it. I expect he’ll have a somewhat more open license,