A single MV licence can be assigned to 1 main domain + multiple test domains.
I want to install same licence to 2 servers behind a load balacer. If I use the same main domain name for second server during installation, will the first server be disabled for the same main domain?
Unless both servers are using the same domain name for the installation and the same database (you can replicate it if you need to), this should not cause any problems. As for test installations, we do not allow more than three test installations per one license. All test installations should have their storefronts closed.