There are special DVD sets released by Bob Ross Inc., each with a particular theme (Seascapes, Mountain Vistas, Forests, etc.) and they have multiple uncut episodes on each disc, but aside from those sets it can be very hard to find complete shows online.
Oh, if you're lucky someone will post some episodes and they might remain on YouTube for a few days or even a week or two, but sooner or later the Ross people will catch wind and have them pulled. Now, brief four-or-five-minute clips? No issues. Those are all over the place and you can find them just about anywhere.