Rather than a rating system, Scratch uses love-its and favorites. Only one love-it can be given by each user, although it is possible for one person to give more than one love-it (see bottom).
Love-its are given to a project when a user likes a project. If the user likes that project very much, a favorite is sometimes given as well. People rarely give favorites without loving the project.
Love-its are sometimes used so when a user gets a certain amount of love-its they will add more to their project, or make a sequel.
While the love-it system generally works well, some people use it as "currency," and only give something if they have a love-it on a project. Large amounts of love-its are sometimes given as prizes for unofficial contests. Some users also just give away "free love-its" instead of only loving what they enjoy.
Also, some people who have multiple alternate accounts can love a project one time per account; this means that one person can love a project several times with enough accounts.
A user can love and favorite his/her own projects. This is discouraged, although some 'popular' users have been known to do it.