The company that produces Lecture 123 has gone out of business, unfortunately. As an alternative, you may wish to consider snapkast (very similar program, that only generates podcasts, rather than the full l123 suite of interfaces), which can be found here. If you wish to still visit the old l123 site, it is here

From l123, January 6, 2009:

Lecture123, the company, is dissolved. However, we are proceeding
to release the code to an open source community. In the interim while
that community comes up to speed, SnapKast is still being sold on
snapkast.com.