No.

I use Penrite HPR Diesel 15 15W/50 Semi Synth in all my bikes. The 10L drums are often on special at Supercheap too.

Depends on the climate/riding conditions and what sort of money you want to spend on oil. Check out manufacturer JASO or API oil spec for your bike and try googling the dr650.zenseeker webpage for a wealth of informative info. I have got nearly 50 thousand on mine and have had no problems using Motul 5100 and Penrite MC 4stroke 10W40 ester based oils. Have also used Penrite MC 10W40 full synthetic in it when it comes on special and roughly 5000km between oil changes.
DON'T use ordinary car engine oils with friction modifiers in them as they can cause havoc with the wet clutch in the DR and you should have no problems.

Gulf western syn-x 3000, 10w40 semi synthetic works fine in a dr650, or any wet clutch motorcycle, there are no friction modifiers in it, and you can pick it up on special for as low as $15.00 for 5 lts .

I personally wouldn't go over the high mark. But remember to have the bike perfectly straight to read it correctly. If it's only over by 1 or 2 mm, then it won't matter. But 5 or more mm over could cause issues with power and seals. Eventually causing leaks and oil burn. It will also create more fuel consumption as engine works harder in a higher than recommended level of oil. The same reason oil viscosity should be a manufacturer specifications.
So remember that it's actually ok to have a engine at halfway fill level. But check the oil 10 minutes after a ride. As need to know warm levels. Usually it's similar to cold but not always.
My DR650 was always at 3/4 or just below full line. I would lean it up against a wall to point it was about to fall off the wall.
Also I always added moreys or similar oil stabilizer. 25%. Supposed to help prevent wear on cold starts but I used it because hot weather here is over 40 Celsius.
Another great addition is to get oil temp gauge or temp gauge to the engine block. I was amazed at times how hot it seemed to get. Especially on 40 plus days with just air cooled engine! !
I loved the dr650. But sold it for more light weight bike because had too many river crossings by myself and picking it up was just getting too hard