Afer reviewing the new Blockchain Defensive Patent License - BPDL, we think it would be beneficial for the community to have a central place for the stratum protocol specification. At the same time, we have been working on a proposal for stratum protocol extensions and associated PR.
Basic Stratum specification
For the time being, the basic/original Stratum Specification is still available through the Slush Pool website. The plan is to migrate this information to this site.
Slush Pool Team