I am sorry, this isn't allowed on frihost. You can't use dolphin.
do you have any other hosts to advise on?
what is this exec exactly?
Dolphin isnt very good anyway,its a good looking script,but look under the bonnet and its a bit of an old banger,if your looking for a good social networking script i would recommend osDate ,it has a good support forum should you run into any problems,plus you can integrate phpbb forums (i think the new version allows you to integrate Vbulletin and smf too) .
exec() is a PHP function, which I think allows you to execute files on the user's computer. It was disallowed here on Frihost due to security issues.