The first lines of source code were added to ZSNES in 2001. Projects with recent activity, and a code base more than five years old are likely solving vital problems and delivering consistent value, and may be organized to reward sustained effort by an engaged team of contributors.
Such a lengthy source control history in conjunction with recent activity may indicate that this code base and community are important enough to attract long-term commitment, and may also indicate a mature and relatively bug-free code base.
Note: The source code for ZSNES might actually be older than the source control history can reveal. Many new projects begin by incorporating a large amount of source code from existing, older projects. You might be able to tell whether this is the case by looking for a rapid rise in the amount of code early in the project's history.