One thing to consider: if the capabilities of your side project would be useful to $dayjob, a sufficiently aggressive company lawyer would be likely to argue t

One thing to consider: if the capabilities of your side project would be useful to $dayjob, a sufficiently aggressive company lawyer would be likely to argue that that makes it "related to our business". (And most of the lawyers I've met would be at least that aggressive, if the company was their client.) If you wind up using that code on the job, the case becomes even more clear cut. So, if you want to keep releasing this code on the side, having something from them explicitly disclaiming (i.e., renouncing) exclusive rights would be very good to have. You've gotten some suggestions about things to look at. There are also open-source projects whose contributor paperwork includes standard employer disclaimers. As to which of these (if any) best fits your situation, you'd probably be best consulting a lawyer of your own.