If you spend your nights rebuilding your company's software as an open source offering, you don't think that would contravene ethics and your obligations to you

If you spend your nights rebuilding your company's software as an open source offering, you don't think that would contravene ethics and your obligations to your employer? Some might argue, "But existing IP and trade secrets protection already covers this". In cases such as this it would be difficult and expensive to pursue a criminal case around IP and trade secrets, so it's cheaper and easier to have a contract clause which approximately restates the same thing but as part of the contract, with some stronger statements to provide added protection. There are plenty of clauses in contracts which might seem odd because they're effectively restating parts of criminal law in the contract, but moving things from criminal law to civil law moves the burden of proof from "Beyond reasonable doubt" to "On the balance of probabilities". Employment contracts are for the benefit of both parties, but ultimately it is the employers who draft them and they will try to get away with as much as possible.