I often work with multiple projects open at a time. If I already have a project open and I go to open another existing project, the newly-opened project window will open behind the project window I was just working on. In other words, the new window does not become active. It's extremely annoying and has led to repo mistakes on multiple occasions.
Is this the normal/intended behavior and if so, can it be changed to force the newly-opened project to become the active window?
Opening other project in foreground is normal behavior.
More likely you have faced a bug. It's already reported on the JetBrains bugtracker and not fixed yet. Here its status, you can check there if somebody has found some workaround, vote up and subscribe for notifications.