You should not list the user "dev1" as a person, who is allowed to do everything on your server, it is dangerous. Instead, you should allow this user to run package managers. For this you need to add the line in visudo like
dev1 ALL = NOPASSWD : /usr/bin/yum, /usr/bin/apt-get, /usr/bin/aptitude
(usually on CentOS people use yum, so I included the path to yum also, but you can remove it if it is not installed on your VPS)
With this setting users will not be asked for password again, when they install something. But if you want to enforce them to type their password again, you can use
dev1 ALL = PASSWD : /usr/bin/yum, /usr/bin/apt-get, /usr/bin/aptitude
Finally, in order not to create a separate line for each user, you can allow all members of the group "users" to install programs (of course, you must trust your users or make a separate group for trusted users)
%users ALL = PASSWD : /usr/bin/yum, /usr/bin/apt-get, /usr/bin/aptitude
Installation can now be done as
$ sudo /usr/bin/yum install name_of_a_program