"Bergdahl has converted to Islam and now describes himself as a mujahid."
You can put some of it down to Stockholm Syndrome, but I don't see his captors putting a weapon into his hands and giving him this much freedom unless they at some point believed that he was one of them.
Clarridge said Eclipse SITREP # 3023, dated Aug. 23, 2012 -- in which a member of the Haqqani network, said to be close to Bergdahl's captors, reported that the American prisoner had declared himself a "mujahid" -- was among the reports provided to Ashley.
"Conditions for Bergdahl have greatly relaxed since the time of the escape. Bergdahl has converted to Islam and now describes himself as a mujahid. Bergdahl enjoys a modicum of freedom, and engages in target practice with the local mujahedeen, firing AK47s. Bergdahl is even allowed to carry a loaded gun on occasion. Bergdahl plays soccer with his guards and bounds around the pitch like a mad man. He appears to be well and happy, and has a noticeable habit of laughing frequently and saying 'Salaam' repeatedly."
At one point -- in late June 2010, after Bergdahl succeeded in one of his escape attempts -- the Haqqani commanders constructed a special metal cage for him, and confined him to it.
The [source] confirmed that the soldier had been missing for five days and when he was recovered, he was a little worse from wear (lack of food; a bit slimmer) but otherwise in good health.
We have some confirmation of the escape attempt. It's probably safe to say that Bergdahl never became a Homeland style covert Jihadist. His brain, which was already scrambled, led him to various extremes.
He can't be described as a committed terrorist, but neither was he remotely a patriotic soldier. Bergdahl had according to reports flirted with joining the Taliban and may have fallen into their hands by trying to do so. It's also fairly certain that he had little idea of what he was in for.
Converting to Islam is not uncommon for prisoners and hostages especially since it's fairly easy, but alternative reports had him celebrating Christmas.
Like his father, I don't think Bergdahl knew what he wanted. Both men are sympathetic to Islam, but like most liberals, have very little clue as to its reality. I don't think that he has come home all the wiser and I wouldn't be too surprised if a year from now he's on the lecture circuit urging us to befriend the Taliban like he did.