It may be the same strong sense of ownership and control that precluded the liberalisation of Truecrypt's license during its lifetime in the past decade.
Perhaps ownership does run deep, even if you've never really released a product for money and it's always been free. Still, it's something I don't understand: If I had a tool that I released for free and finally gave up on it, I'd like to think I'd open it up under an exceptionally liberal license or just dump it in the public domain. That'd be especially true if it had a lot of users.
That's what makes me think that if this isn't some elaborate scheme it's likely the result of some sort of legal requirement or action (e.g. Lavabit) which would preclude the author(s) from doing anything else with the software. It's a shame they couldn't take a scorched earth-esque approach of dumping everything in the public domain, including notes on why this was happening, everyone else be damned, but I'd imagine their entire career might be in jeopardy at that point (and possibly their freedom).
Given that border searches of electronic hardware are becoming more commonplace in the US, I should think that something like this is important. I know when I was driving back and forth to university, the thought crossed my mind when I had my laptop with me as I went through the border patrol checkpoint that there wasn't anything much I could do (outside lawyering up) if they took it upon themselves to grab it and search. Sure, the worst they could have done was read my email (and maybe clear out the junk folder for me while they're at it), but it was the principle of feeling so violated by the act itself that drove me to stuff all my school work into a TrueCrypt volume.
(This was years ago, and TC was the best option for XP. Though I later switched the laptop over to Linux.)