To install Vacation:

First edit Makefile and change your PREFIX to set where it should go (it
defaults to /usr at the moment, you may want /usr/local instead).

Now under Linux type 'make' and under FreeBSD type 'gmake' to compile
the program.   To install it you will need to do (as root) 'make install'
or, for FreeBSD, 'gmake install'.

That should install both the vacation binary and the man page to the
desired location.

If you are using SELinux you may find that you need to relax the Postfix
SELinux policy slightly to get vacation to work.  It has been reported
that the following rules fix things up on CentOS.

#============= postfix_local_t ==============
allow postfix_local_t sendmail_exec_t:file execute;

#============= postfix_postdrop_t ==============
allow postfix_postdrop_t postfix_local_t:unix_stream_socket { read write getattr };

N.B. If you encounter any difficulty in installing vacation, let me know.

For more info about the programs, see the man pages.