You're correct. The sodium salt of DNP is what bodybuilders refer to as "crystal DNP." Pure DNP, or the DNP base, is commonly referred to as "DNP powder."
There are a lot of myths about how the two forms differ, similar to the myths bodybuilders have about how testosterone enanthate and testosterone cypionate differ from each other. In reality, they are going to act very much the same. The primary difference is that crystal DNP is slightly weaker than powder DNP, since it is not pure DNP, but contains a sodium molecule. When the sodium is cleaved, you're left with the same DNP base that you get when you take DNP powder. Both forms are highly bioavailable, which is not surprising considering DNP is a small molecule that can even permeate skin. It's often been said that crystal DNP is 75% as strong as powder DNP, but based on the chemical structures and molar masses, it looks like crystal DNP is about 89% as strong as powder DNP (molar mass of 184.106 for powder vs 206.088 for crystal).
Hope that helps,
Conciliator