Folks at my company have had the same problem. I think it's a big mistake to not allow simultaneous installations of V2 and V3 trial. Right now, I have too much work invested in V2 to be willing to put it at risk and try V3. As a result, I haven't even looked at V3, which I was really looking forward to.
We are sorry for the inconvenience. ForeUI V3 does not distinguish license by version, instead it check the age of the license to decide if it is valid. That's why V3 read and write license information that is shared by V2.
If you forgot your V2 license key, please contact us (firstname.lastname@example.org) and we will try to help.