I just noticed that psp.akop.org had been broken; this has probably been the case since last week, when my host switched servers. The switch to a new server apparently broke my Rails installation, which in turn broke the application that runs the site.
In any case, this has been fixed, and downloads are accessible again.
March 13 Site was down again for a while (thanks Carl); should be back up now (I hope for good)
I'm a programmer with too much interest in programming, and not enough time.