You could always be nice and do it one of two ways:
First choice, sell the theme and have big notices saying that users will need to purchase the extra plugins/scripts and give them the links to the real suppliers stores or carts or at least sites. That way you will be selling your product as well as helping the other authors sell their products.
Second choice, contact the authors of the other plugins/scripts and ask what they can do for volume licensing or special deals if you purchase a licence every time you sell a theme. This would be harder as it relies on you to do the right thing every time you make a sale.
As far as this goes it's less of a legal issue, and more of an ethicla issue. The big point is how would you fele when someone takes your theme and gives it away without you making anything from it?