"...I don’t think anyone’s talking about not providing the agreed upon services..."
Really? So, if there is a meeting at one of my companies, and a meeting at another of my companies, I am going to make one of them wait and push their deliverable or solution out because they had to reschedule their meeting where I am a necessary resource?
Yes. I am from a different time. This is dishonest. Because while it ISN'T unscrupulous to hold down two or three jobs, you CANNOT rationalize it UNLESS YOU HAVE CLEARED THIS WITH YOUR EMPLOYER IN ADVANCE, which I am certain the people who do this DON'T do.
It is dishonest. Unless your employer is aware this is what you are doing, it is rationalization of blatant dishonesty.
Until they start clearing their plans with me, I feel no need to clear mine with them. As long as the work is done, they should have no issue with how I spend my time. And the work being done includes attendance at all necessary meetings, etc.