Copyprotection is very unusual in the linux world.
Regarding the technical details: There is no registry in linux, usually program settings are written either to a file/directory in /etc/"application name" or in the user's home directory (home directory entries are usually hidden, to avoid clobbering the directory with hundreds of files)
However, all of these files can easily be changed by the user, so a copy protection scheme is not easy to implement. Also keep in mind that most linux users are quite savvy and will take such a copy protection as a challenge.
You should also be aware of the licence issues involved. If yu want to apply a restrictive license to your software, you must not use code that is distributed under the Gnu Public License. You may however use the Gnu Compiler.