DSLX was never and has never been a CLEC. They were and are a wholesale ISP. And now they're basically a reseller of Ikano their parent company (formally Dial-up USA). Anyone can become a DSLX over night with $200 and a call to them.
Earthlink/Earthlink Carrier/Wholesale, MegaPath, Sonic,net and a few others are CLECs that are still around. Otherwise you get wholesale companies and nothing more.