Free is a misnomer, tests find the same aquatious stuff in your intestines after drinking Splenda sweetened beverages as you would find after drinking typical municipal water.
And Only in certain people and in very small amounts.
The long standing belief that Splenda is completely unabsorbable is simply incorrect but how absorbable varies widely person to person.
What affects a small amount of Splenda being absorbed has is unknown, definitely no near term side affects have been found.
So Chlorinated Tap water and Splenda sweetened beverages have nearly identical affects on the number and type of gut bacteria.
Whether this matters to you or not is another debate, certainly far safer than aspirtame which honestly should just be banned due to its overall instability, especially in warm weather