That's part of what FOSS people mean by free/libre. The user (which may be a company) is not restricted in what they do with the software and source code. If it's copyleft, then the only restriction is share-alike/that it remains libre and open. So that includes the right to make a profit.

There are non-FOSS licences you can use if you only want non-commercial use, or want to apply various restrictions whilst still keeping things foss-like (in the sense that most people can e.g. fork it and generally do what they want with it, but in some scenarios/to some users it will not be foss), but they aren't considered FOSS.