[kls]

Is this essentially "unofficially okay"

I would make it officially OK and inform my potential employer of the intent to do work outside of your agreement with them. Above board is always better. A word of advice though once you have an official OK in writing, don't talk about your other work at your job. You can read the famous story of Woz, the Apple 1 and HP for the reasoning why you should not. In short they said they where not interested, he built it and then they wanted a slice of the pie. It's better to get it in writing before any side projects and then never mention it again.

[hrowthr]

Thanks! If I understand correctly, I should get a one-time official OK in writing before I join, and then I use my own judgment when deciding to do some consulting (to make sure there's no conflicts of interest)? Or do I get an official OK in writing before every gig?

This is what my non-compete clause roughly says:

Duty not to compete: My work at the company requires my undivided attention. I will not, without the company's written consent, engage in any other business that directly competes with the company, uses any of the company's materials, or otherwise conflicts with the company's business interests.

[kls]

One time, and honor the non-compete I would use the written consent as the reason to get it in writing, just say you want to cover your bases up front and you would like it in writing that so long as the project does not engage in the "core" business that their is no conflict of interest. With IT type jobs almost everything can be construed as a conflict of interest because everyone has IT as a part of business that is why you want to explicitly call out the core business what ever it is. If it is travel you want to say travel if it is real estate you want to call out real estate and you want to try to constrain it down to the most focused segment that you can for example if they do commercial real estate rental you want to state long term, commercial real estate rental. Avoid vagaries.