Final Draft 13 comes with an unlimited number of installs but the retail license allows two computers (that you own and operate) to run at a given time. If you have (for example) five computers, FD can be installed on all of them and you can sign in and out of Final Draft on each one as needed (up to two machines simultaneously).
Signing out of Final Draft on a computer temporarily disables the program but allows you to sign in on another computer. Signing out leaves the installation and all of your Final Draft scripts on the machine and fully usable once you've signed back in.
To sign out of Final Draft, go to Help > Sign Out (internet connection required).
Final Draft, A Cast & Crew Entertainment Company, does not have the ability to remotely sign anyone in or out of the program on any computer.
Multiple-user site licenses allow for X number of computers to run Final Draft, per the terms of the sale.