In OpenShift Express you can actually only create 5 applications. In the tooling, if you try to create the 6th, the tooling would report you that the 6th app could not be configured.

It unfortunately does not tell you that there is a limit of 5 applications. We should tell the user that he can only create 5 applications.
The backend (the REST service) actually reports that you can only create 5 apps:

org.jboss.tools.openshift.express.internal.client.httpclient.BadRequestException:

{"debug":"Validating application limit toolsjboss@gmail.com: num of apps(5) must be < app limit(5)\n","data":null,"messages":"","broker_c":["namespace","rhlogin","ssh","app_uuid","debug","alter","cartridge","cart_type","action","app_name","api"],"api":"1.1.1","result":"toolsjboss@gmail.com has already reached the application limit of 5","api_c":["placeholder"],"exit_code":104,"broker":"1.1.1"}