Is DB15 the same as VGA/HD15?

Technically, no, it is different. DB15 is wider and has 15 pins in two rows of 7 and 8, while VGA, HD15 or DE15 (names are interchangeable) is a smaller connector that has 3 rows of 5. However, some devices and manuals will inaccurately label VGA connectors as DB15's.