Hi we have a client who has a database built in DataEase Plus 3.5. Is there any support for this or options for migration

We assume the version you are talking about is NetPlus 3.5?

This product was never a DataEase product but was originally developed as DataEase Professional but was sold to Symantec before it was released. It was released under different names like Enterprise Developer etc. until Sapphire the then owner of DataEase bought it back and released it as NetPlus. 

The product is no longer maintained or supported and is currently owned by a big user of the technology.

We did help this client with developing a new driver for Microsoft SQL Server about a year ago which they needed to move forward with their clients.

There is no sensible migration path but obviously due to its similarities with DataEase for WIndows a redevelopment in DataEase is quite straight forward.