I have conflicting answers from vendors whether venting a dust collector directly outside will harm the DC motor. Make up air is not a problem. I can discharge into a field, and nearest neighbor is 1/4 mile away. I would like to avoid the cost and cleaning considerations of filter bags/cannisters.
I think it depends on the machine. Many dust collector motors are designed to run against a certain amount of resistance provided by the actual dust collecting parts.
My system wouldn't work the way you intend because of the design, however, my dad's dust collector is basically a large fan mounted on the wall. His is designed to do what you appear to want, however, he couldn't just let it vent straight out with the 8" pipe it was designed for. He ended up having to constrict it down to a 4" pipe so there was enough resistance he wouldn't burn out the motor. The other option was to give it about 20' of pipe to push the dust through, which wasn't convenient.
So the answer is both yes and no. Yes if you just vent it straight out you could severely damage your motor after some use. However, there are ways to fix the problem. I would recommend getting the help of an electrician to figure out the load balance needed but it can be done without damaging your motor.
For most fans, if you restrict the exhaust, the fan will turn slower as the motor tries to push the air it sucked in against the restriction.
If you have an unrestricted open exhaust and for some reason the inlet gets clogged, likely occurrence for a dust collector, the impeller will spin up to the unloaded speed (almost) of the motor. As there is less air for the blower to process, there is also less air friction, it is basically running in the partial vacuum it created.
If the impeller or motor is not rated for operating that speed, damage could occur.
I think DC motors without speed controllers have that problem most often.