It is glad to hear that Ubuntu 15.04 is released today. We download the latest 64bit version and install it in virtualbox to test our new miniSIPServer V20 version.
We are very glad that it is no problem to run miniSIPServer V20 on this Ubuntu version. So you can enjoy it yourself if you want to try latest Ubuntu 15.04.
Of course, since 15.04 is not LTS version and is not recommanded to most customers, we suggest you to stay with LTS Ubuntu, such as 12.04 or 14.04.