I agree with you mostly<g>. Modify your point:

>6.a) Will you be able (not only capable but will you be able to make the time) and willing (will you want to do it) to update your own framework as new versions of Visual Foxpro are released?

6.b) Are you sure the vendor will switch at the same time as you to newer versions ? Are you sure you can port the framework yourself if the vendor goes out of business ?

Even then, the benefits outweigh the risks at least tenfold IMHO.

regards

thomas