Greetings,
If its only to execute start/stop script for an application, why not write 2 scripts that Greg can execute (one for start and the other for stop)
e.g. start_appl and stop_appl
then in sudoers:

greg ALL=/usr/bin/su - devuser -c st*_appl

Thanks Vbe;
But your solution is not what i'm looking for, as i may need to add more commands for that user and may be other users. If you read my last reply you will see the last 2 things i'm looking for

this is not how sudo works. sudo is designed to give access to a limited amount of commands.

Based on your requirements you should just give him the account password and have him use su. There is no benefit to allowed greg to run a shell with sudo.

I agree with Franck: It is not to be done with sudo...
Your alternatives now will lead to other issues such as "as" devuser you cannot stop Greg to change devuser's password for instance or to modify the .profile etc...
Secondly, you would have to modify (and test) the .profile to take in account who (and from where...) is logging onto the account and send it to another history file..

But what you are trying to do can be done quite easily...
Just add a .rhost in devuser's home directory wiht the name of the box and greg.

Greg can then use the account with no passwd by typing :
remsh or rlogin
e.g. with remsh (or rsh depending of your *ix flavour)
remsh yourboxname -l devuser


All the best
Vic