A Helix Professional Developer is a person who can be relied upon to come into your home or place of business, either live or remote, and fix a particular problem you're having with your Helix application. In addition, he or she has the skills to design, implement, document and support a Helix application. End-to-end lifecycle management, as they say.
A Helix Solutions Provider is such because he or she provides a Helix Solution. More to come (watch this space...)
It is our belief that a certification process is needed for Helix professionals. Until Helix 6 is complete, however, there will be no "work" done on this issue beyond what may be presented in the Forums.