The Stoics of the Roman Era Collection description page says it is from the Perseus Digital Library.

Why should we pay again for something that is already available for free?
I checked the contents of this collection against the Perseus Classics Collection, and the works of Seneca and Epictetus are in both (I think), but the works of Marcus Aurelius appear to be only in this one.
Still it's puzzling that this says it's from the Perseus Digital Library at the top of the page, but then on the actual books it says they are from the Loeb Classical Library. Is there some collaboration between those two library producers?