That's possible, however the idea is that the net outcome would be positive. Say city A open sources some useful software that city B, C and D freely copy and d

That's possible, however the idea is that the net outcome would be positive. Say city A open sources some useful software that city B, C and D freely copy and do not contribute anything back. No harm is done to city A open sourcing the software they would have needed anyways. Then city E starts using the software and needs some additional functionality so they use the budget they would have otherwise used to re-implement their own proprietary version of the software to contribute back their enhancement to city A's project. Sure some cities will not contribute back but in open source it is the organizations most in need and most able to contribute back who do. Why is that a problem?