I have a different thought process on infidelity with regards to the show and Dev and Sona.
Whether legally divorced or not, both of them separated 7 years ago. Dev chose to drown himself in alcohol and seeking pleasure or say respite in the company of several women. Sona, since not shown to us, has probably not indulged in either of it.
To me, it's fair - out of sight, out of mind, life goes on - so in practicality of life, it's fine what Dev chose for himself. Marriage was over in their hearts, whether on paper or not doesn't matter and therefore I don't think it can be termed as cheating.
In current scenario, when both are back in business of love with each other, or given what they shared in the past, if they do indulge in seeking pleasure in another person (mental or physical) then I would term it as cheating.
In real life, it will be hard to believe that Dev who was so madly deeply in love would move on for sexual pleasures, and there is absolutely no possibility of them getting back together. But this is fiction, love conquers all... And rest of the emotional stuff will be fed in, you see!
Edited by sia.krpkab - 8 years ago