We haven't seen this confirmed anywhere else yet, so for now it's still just a source reporting. But it does make sense. The Cowboys also looked at vet Garrett Reynolds a week ago, so they are definitely in the market for depth at guard.
Nwaneri was a starter for the Jags since 2008 but was released in early March. He is 30-years-old and had received minimal interest on the free agent market. Nwaneri was a fifth-round pick out of Purdue in 2007 by the Jags, and only missed five starts in his career showing impressive durability. Nwaneri is from the Dallas area so that might have been part of the reason he could end up signing with the Cowboys.
The speculation would be that he will compete for a backup guard spot, along with the loser of the Mackenzy Bernadeau/Ron Leary battle at left guard. Bernadeau is probably also being looked at as the backup up center, so Nwaneri could also fit in nicely as depth along with a swing offensive tackle.