How many people can register a copy of Final Draft?
One. Only one person can be the owner of an individual copy of Final Draft. That number again: One.
Even if two (or more) people split the cost of the program, only one person is allowed to used the program. One person can register and that person is the legal owner of the license. The person who registers first wins.
For more information, see I'm using someone else's copy of Final Draft. Can I get support?