Does Hubble withhold information from the public?

No. Information and images taken by Hubble Space Telescope are not withheld, but they do take time to get to the public.

Many of the images taken by Hubble are never formally released to the public because they are typically only of interest to the scientific community. Full access to these data, which can be processed into viewable images, is available online via the Hubble Data Archive. The archive's mission is to serve the scientific community. It may not be useful to or easily operated by the general user.

Hubble images produced by the Space Telescope Science Institute are covered by copyright law, as stated on our Web site at http://hubblesite.org/copyright/. This copyright covers most images displayed on all of our Web sites.

Here is the scoop on why it takes time to get the photos out to the public.

The areas of the sky and the objects that Hubble's various optical and spectrographic cameras take pictures of are very carefully planned and scheduled. Scientists from universities and scientific institutions prepare proposals to use the telescope. If their proposal is accepted, time on the telescope is scheduled. Once the scientists have their raw data from the telescope, they then have one year in which to conduct their research and prepare papers. After this one year, the information becomes available to the public.

Sometimes “Early Release Observations” are released to the public, as is the case when a new instrument is installed. Photos are then released as soon as possible after the installation to let the world know that the camera is performing up to its expectations.

If you would like to see a "scrapbook" of photos, as they look when they are "translated" from the original digitalized pixels sent from the instruments aboard the Hubble, you can see them at the MAST Scrapbook:
http://archive.stsci.edu/scrapbook.php

Again, these are photos that have become available after the one-year grace period for the astronomers.