the max weight without screwing is 150kg with screwing to the door 300kg. It is also stated that you should not make the exercises which have twisting impact on handle when it is not screwed as it can loosen it.

"...metal brackets for optional permanent fixing with screws, maximum load capacity with fixing material up to 350kg (without up to 150kg)ATTENTION: Due to the construction of this item it is forbidden to do exercises which have twisting impact on the bar (e.g. field swing or similar). The rotational movements may cause the internal thread of the pole to untwist and the pole may come loose, resulting in serious injury.The pole is not designed to be attached to and used for e.g. children's swings or similar.
Improper use of the pull-up bar is at your own risk! "

The pull-up bar is extended by twisting the ends to fit tightly into the door frame. Screwing is possible but not necessary (so long as you extend the bar enough for a tight fit). I haven't screwed it into my door frame and it supports my weight fine.