Hello for ubuntu there is a ppa with 2.5.3 if you are using ubuntu 12.04 or 14.04
https://help.ubuntu.com/community/Firebird2.5 https://help.ubuntu.com/community/Firebird2.5 Also you can use firebird server 2.5.3 installed from tar.gz with fbclient 2.5.x installed by flamerobin as dependency
