If we further assume that the two companies who produce the two products only produce those products, then for those two companies it's zero sum for them to contribute in good faith to open source bloom filters. Any gain that one company gets in the quality of their bloom filter is likely to translate directly into fewer customers for the other.

It isn't globally zero-sum, notably the users of these companies' products are presumably better off, as are other software projects and their users who might benefit from any improvements made to open source bloom filters.