Open source is not consistent with broad restrictions on usage in that manner. It is a perfect example of the software developer reaching into the business of the person using the software and telling them how to do so. This is precisely the sort of thing that open source (and previously free/libre software) was created to get away from.

Don't you agree that any improvements to the code should benefit the community that built it?

Yes in general, but it is debatable whether requiring that is beneficial overall. This debate is long-running in the open source community and I won't repeat it. However, if that is your goal then use something like the AGPL which requires that improvements to the code be given back to the Steem community (which the Steem community can then decide whether or not to adopt) whether or not the person making and using those improvements herself wants to to be part of the Steem community.