The federal government expects that researchers on sponsored project will have some effort, charged to the agency or as a cost share. Here is how the Office of Management and Budget describes it:
While the phrase 'letter of commitment' is often used interchangeably with 'letter of support,' there is a fundamental difference between the two. A letter of support may, for example, state that a community group endorses or approves of a particular project. A letter of commitment, on the other hand, is a statement of active participation in the project. It specifies resources that the group will commit to the project and identifies what role it will play in bringing the project to a successful conclusion.