I think your HSQL URL is wrong. It should also include the database name,
so something like
jdbc:hsqldb:hsql://localhost/mydatabase
if mydatabase is the name of your DB (file). Not including this can (I'm not sure if it is the case here) confuse the parsing of the URL, which may lead to the DriverManagerDS thinking that your driver is not suitable (it is found, but it thinks it is not a good one)