umx depends on OpenMx.

OpenMx currently lives on \url{http://openmx.psyc.virginia.edu} rather than CRAN so, to install it use

source('http://openmx.psyc.virginia.edu/getOpenMx.R')

This will download and install OpenMx!

MORE INFO

See the umx and OpenMx home pages for more.

 - (\url{http://github.com/tbates/umx})
  - (\url{http://openmx.psyc.virginia.edu})