Should be fine. I've got no end of creatures in my bin although none as large as a millipede. And in outdoor bins you'll be getting these creatures whether you like it or not and the worms still do fine. It can be a good thing as different creatures get attracted to different foodstuffs. In some cases an issue might be competition for food, black soldier flies for example.

competition for food is not a problem i have tons of food i am just worried the millipedes will excrete that so called toxic liquid on the worms and kill them off.

Millipedes shouldnt be a problem since they are detritivores...pretty much like worms. The ony issue I would be concerned with is taking steps to ensure that they are not allowed to run rampant in your soil that you transplant the harvested vermicompost to if you will be growing seedlings and young plants. If I understand things correctly, millipedes being detritivores will typically feed on decaying plant matter but will also readily go after young plants and seeds. Up until that point though, they should be a pretty good addition to the vermicomposting effort.

yea i believe i read that up somewhere as well. i got my millipedes in my garden we keep out compost pile their so their is more food for them to handle. and it is an endless supply due to trimming anyways.