It all depends, is the developer on a contract to provide the portal or is the developer a company employee, if the developer is a contractor was it specified in the contract that ALL code submitted must be supplied with UML diagrams or is it something that has been asked for later?
- If the developer is a contractor and it WAS specifed that all code submitted must be supplied with UML diagrams then you could say that the developer has access to the open source code so must produce UML diagrams for it or they don't get final payment.(depend on how much of a hardass you want to be)
- If the developer is a contractor and it was NOT specified that all code must be supplied with UML diagrams then the developer does not have to supply them so long as they have carried out all contractual obligations.
- If the developer is a full time company employee, then you could say get the code and produce the UML diagrams, however you would need to balance this out with how important it is to have the diagrams v's how long it will take to produce.