In [my post on when it is appropriate to reinvent the wheel](http://stackoverflow.com/questions/18428/what-considerations-should-be-made-before-reinventing-the-wheel/1951913#1951913) I list a number of advantages of a reimplementation. I think those advantages apply especially for framework libraries. For example, it is often impossible to isolate the use of a framework library inside a small part of you application. Instead, they tend to dictate the structure of the client source code, and therefore it is desirable to have [full control](https://softwareengineering.stackexchange.com/questions/29513/is-reinventing-the-wheel-really-all-that-bad/29527#29527) over the library.