@rahul
For legal point of view you have to wait till divorce.
You said,"her divorce case is pending in court since 5y "
Very long time why?
Again you said that,"
She filed for divorce and he is saying that he will not give divorce forever.
In these circumstances, is there any legal implication on me from her husband side?"
What it means?
Just wait for divorce otherwise if husband take some legal action in future then you are in trouble.Law doesnt permit this.Your main problem is as you said earlier ,"
IVF or sperm bank are not disclosing the identity of doner to the receiving lady."
If they are not disclosing it and in future she produce baby and suppose husband file case against you and through DNA test you are in trouble Right?
Better to adopt a baby .I agree with Jamai Of Law's view ,"Still there is no guarantee that husband would complain about it!"