In the past, I worked on a project for Luxembourg's CTIE (their IT administration). In most cases, they explicitly requested that we reimplemented features we needed instead of including more third party libraries. They just allowed essential libraries for the project, like Struts for the Web framework, or implementations of standard libraries like JPA, JTA etc. that came with WebSphere. Everything else, we had to reimplement. For them, it was just much easier to manage, given the amount of systems they have to manage. And the allowed libraries were only allowed in versions that they had reviewed before for security issues. In the end, reimplementing features/functions that we could have included with other libraries was never a reason for any problem : this practice requires some additional work, but has never been significant for the ability to deliver the project as expected.