I don't know about other publishers, but with the material from WOTC, it only includes the digital content. Also, if that content is purchased here on Roll20, it's only usable here on Roll20; you can't access that content if you aren't logged in. AFAIK, it's the same for their digital publications on <that other site that I'm not sure I can mention here>, you can only use it on that site and not here. Reciprocally, if you buy their physical books you don't get access to any of their digital content. That is why I can't consider moving to a VTT other than here: I can't afford to spend that much money *again* to re-buy all that material.