blueray players are essentially all-in-one units that combine a reader, processing hardware, and software to decode said media disks. typically the drive is read-only.
pc blueray drives are just the drive itself with whatever drivers are required for windows to recognize the unit. i'm not sure if they make a read-only drive, all i have seen are read/write (burners) on the market.
the same is true with regular dvd drives: you need decoding software to play movies with the drive. i know windows 7 has dvd decoding software integrated into media player but i'm not sure if it supports blueray. as for vista,xp,older you might need software. i've always liked cyberlink powerdvd for ease of use, but i haven't used it in over a year (i have win7 now).
An internal Blu-Ray drive does NOT come with an HDMI port that connects to your TV. There is no reason for it to have once, since it's not SUPPOSED to connect to your TV, it's supposed to connect to your motherboard via a SATA port.
Since it has no HDMI (or component or composite) outputs, there's absolutely no need for it to be able to decode and "play" video using any of the standard video formats (480i, 480p, 720p, 1080i, etc.). There's no connector on the drive through which those formats could be sent. The SATA connector only transmits raw data bits to the motherboard.
It's up to software running on the computer system to read the raw data coming from the drive, decode it into a series of frames, and send those frames to the video card where they can be displayed on the system's monitor (or be packaged into an HDMI stream for transmission to a TV set).