In my opinion the best way to contribute to ReactOS is by buying a copy of Crossover Office or Crossover Games. Besides actually getting something immediately useful, you're directly contributing to the development of WINE. ReactOS uses WINE for most of its non-kernel code.
The funding is to pay for full-time ReactOS development. Wine might be involved to a degree, but surely putting money directly into ReactOS is the best option.
Serious question: If Oracle wins their lawsuit and the court rules that APIs are indeed patentable, what prevents the ReactOS team from being sued into oblivion by Microsoft?