What is the REAL risk of receptive oral sex WITHOUT ejaculation, by a person who has ordinary bleeding gums?

I'm not sure what you mean by "real risk".

The bottom line is this: if any HIV infected fluids (like semen or pre-cum) come into contact with your mucous membranes (like the lining of the urethra, vagina, rectum, or mouth), there is a risk for transmission. The actual likelihood of transmission is a different story, and difficult to quantify.

The risk of HIV transmission through oral sex is low when compared to unprotected vaginal and anal sex. The reasons for this, in part, have to do with biological differences: simply put, HIV seems to have a more difficult time causing infection when introduced to the mucous membranes of the mouth (saliva may provide additional protection and the cells in the mouth may not be as prone to infection).

Performing oral sex on an HIV positive man does pose a risk, albeit small, for transmission. Most studies to date say that the risk of infection through fellatio is low, and a recent study showed that the risk was almost negligible. Getting his semen in your mouth increases that risk. Ejaculation in the mouth probably accounts for most cases of transmission through oral sex. Other factors, like the condition of your oral health, your immune response, and his viral load, may have some role in the likelihood of transmission when performing oral sex.

See What You Should Know About Oral Sex for more information.

RMK