First of all NEVER DO ANYTHING TO THE /TMP DIRECTORY!!!!! I cannot stress this enough. Doing so could damage your install. The OS uses this directory as its workspace.

Second, CentOS now has proftpd on yum, I believe it is on the RPMForge repo.
View how to add this repo HERE.

For those who are security minded and do no click links here you go:

http://wiki.centos.org/AdditionalResources/Repositories/RPMForge

Or just Google for centos RPMForge.