DANTES stands for Defense Activity for Non-Traditional Education Support. It's a Department of Defense program that comprises a whole range of things, including certification programs, tuition assistance, distance learning programs... and the DANTES Subject Standardized Tests, or DSSTs. So it's probably better to call them DSSTs, but saying "DANTES tests" certainly isn't wrong. They've been open to the civilian public for quite some time now -- I don't know exactly how long. You can visit
DSST - GetCollegeCredit.com to find out more about the program, and find a local testing center. I strongly advise that you try to find an Internet-based testing center near you. Taking the paper-and-pencil exams means having to wait for your scores -- too much stress for me.
-Gary-