Under the effect it states that you create and throw the javelin. Is it the magic propelling it or do you have to have a hand free and actually throw it. I have an idea for a character and was wondering if he needed to keep one hand free or if he could do it with his sword in hand. I had the image of him chunking the javelin atlatl style using the sword, but I'd rather keep it within the intent of the rules. The only mechanical advantage is a bit of time savings on draw/sheathing the sword.

IIRC, it is a thrown weapon so you need on hand free to throw it like a javalin. You can have a sword in the other hand, but you can't be dual-wielding.