Sir there are a few scripts which generate warnings and errors on PHP 5.3+ hence we have added a check to not allow users running PHP 5.3+ to install scripts as it will display errors on the site.
These scripts are not compatible and even if you install manually it will give you the same errors. Whenever there is an update in this script and they work fine on PHP 5.3+ we will remove this check and then you can install it on PHP 5.3+