It's very legit, fwiw. Lisa Waters is awesome, and took over editorial duties from MZB when her estate finally got its collective head out its collective ass after she passed away. Some major fantasy authors got their starts in this series, or had their nascent careers boosted significantly. Don't panic too much about the deadline. She puts out new volumes periodically, so there ought to be more chances in the future. Do make the effort! It's worth it, and the recognition can help a lot.

I'll see if I can find my old copy of MZB's guidelines for submission, though I'd not hold my breath. >.< I think that box is in (overlocked...) storage. Definitely do read What Is a Short Story? and Why Did My Story Get Rejected?, both guidelines that MZB wrote to educate authors with whom she worked. There are others on the Marion Zimmer Bradley Literary Works Trust site, but those two, and the specific submission guidelines listed in the above link, are the most important. Always read the submission guidelines!!