This practice isn't what copyright was intended for when it was written into the constitution. The idea is that copyright is a time-limited monopoly to make money of immaterial property, it mustn't serve to lock out the secondary market for printer cartridges and coffee.
The way it should work is, Keurig should be able to do whatever they want in terms of DRM on their hardware, and other companies should be able to do whatever they want in terms of reverse engineering that DRM to produce compatible products.
I don't know if that's how the law actually is, but it sounds like it might be.
It's illegal for them to reverse engineer (and reimplement) hardware DRM for interoperability, but software DRM circumvention is protected by DMCA, only for the purpose of interoperability.
In my jurisdiction, interoperability is a valid legal reason to ignore copyright restriction. Actually, I believe that none of the current global copyright agreements would prohibit anyone from distributing products that flagrantly circumvent that DRM, there's only the USA-specific DMCA.
