I am typically defensively strict in the legal issues. No matter if that application were developed by an employed developer with a MAXFRAME license the company bought or by an external contracted to deliver not only binaries but also source code of a project, it would be entirely legal to continue work on this with another external developer. As framework vendor, you would just hinder the success of your framework, if the distribution of its libraries would be restricted, as no serious company will order a custom made software without having the source code for the case of later extending it or fixing problems after warranty. Framework vendors surely have means to keep wizards and builders and other tools helpful for the setup of an application project, but restricting the distribution of libraries would compare to not allowing distribution of runtimes.
It's true that the framework libraries contain intellectual property and you could choose to protect that by only providing binary parts, but it'd be so restrictive, that you risk the business success of a framework.
That said an update of the framework still won't bring up all other code to VFP9 compatibility and might fix some version problems, but introduce new interoperation problems anyway. VFP has some settings allowing downward compatibility, especially REPORTBEHAVIOR, ENGINEBEHAVIOR and SYS(2700). If I were you, I'd try if those fix most problems and stay with the codebase, as good it would be to upgrade the framework itself for future extensions. Don't expect a new version of the framework to fix all problems anyway. Managing to get the project working with the compatibility settings will be your major test, whether the project sources are complete and working without needing VFP6. I am struggling with a project I only have sources of the main application EXE and there are at least three other EXE and DLLs I have to use as is. Fortunately, that system is VFP9, but the customer has no idea, whether other binaries are VFP at all, could also be third party tools used. I know how to detect VFP binaries, so I could probe them, but it won't bring up their sources.
Bye, Olaf.