I have this commercial product that I want to distribute and I just want to know if I'm supposed to put your logo in a prominent place on my product? We can mention your product in our marketing material but to have "Powered by HSQLDB" on main page is an absolute no-no. If this is the case then well have to go with Firebird.
This is a late answer but for future reference, you do not need to put our logo or "Powered by HSQLDB" anywhere in your product. You should include our licenses (hypersonic_lic.txt and and hsqldb_lic.txt) in your product's documentation.