What are the main differences between SQLite and HSQLDB? There are lots of applications using both of them, but I don't really see any major difference.
SQLite is implemented in C, HSQL is implemented in Java.
It should be more seamless and easy to integrate SQLite with an application project written in C or C++, whereas I would expect the HSQL technology is easier to integrate with a project written in Java.
No doubt there are numerous other more subtle differences between these two embedded databases, but the above is the most prominent difference.