Parry is a job synchronization server for high performance computing. It can handle job sharing among several clusters, and is especially helpful in cases where the network cannot be trusted, and when time resources are limited.
The source code of Parry, and the protocol it implements, are proven in a paper available here. Like anything guaranteeing desirable properties, the integrality of Parry's source code is open source (GPL).
The domain where Parry is useful is the case of "re-sharable" jobs, like in the exploration of tree-like spaces. See the example page for a typical use case.
Parry exists in two flavors: the original one in Haskell, and another one in OCaml. There is no obligation to use neither of these languages, although resharing jobs is probably easier using these two languages. If you are in doubt, the OCaml version is likely to be faster, due to its smaller bandwidth requirements and the smaller size of binaries produced by ocamlopt.