If it's not WSDL, then my guess is WYPR. 106.5 can put a better signal into Salisbury than 106.9. Also, WSDL doesn't reach down to Pocomoke (not yet anyway, although WSCL/WSDL have applied for 88.9 down there if I remember correctly) so maybe WYPR thinks this is a good area to expand into. They seem aggressive. (I'm not sure why they bought 106.9 in Ocean City in the first place, though, since WSDL was already there first and now they're duplicating most of that programming, and I doubt they're getting much out of it.)
It can't be WESM which already has an excellent signal in that area.
And as for WAMU, someone at DCRTV said that American University's new Delmarva station at 88.3, WRAU, will be part of a Christian alternative rock network, not a relay of WAMU. The WRAU page at Radio-Locator seems to bear this out. If true, I guess WAMU figured that triplicating most of the same NPR talk programming on the Shore is a lost cause, but why Christian alternative? Why not put their bluegrass channel on there, or AAA? I didn't realize that American University was that religious. Or did they cut a deal with the Christian broadcasters with whom they were fighting over the 88.3 frequency for years and years and years?