By company policy you are prohibited to work in any other place, which I think is a violation of your rights. What you do in your spare time, is your own business. (Of course if you are not using company knowledge to help competitors. That one is a no brainer). Especially in some situations where you really need extra money and need an extra job.
As a developer, some of the projects you get may be dull and built on old technologies but you can always pass up on those and choose different ones.