Ok, that got me curious so I did a search to see what IMDB required to list a work on their site.
I don't think it needs to be commercially released. It only needs to be of interest to the general public.
From what I read, charging for it doesn't meet that requirement. Making it available to the public may though on a technicality since you're distributing it on Amazon. I would guess you don't even need to sell a single copy in that case.
Here is what I found in their help files:
Eligibility: General Public Interest
For a work to be eligible for inclusion in the database it must be of general public interest and should be available to the public or have been available in the past. We accept most kinds of films/TV shows, including big screen and direct-to-DVD features; documentaries; experimental films and short films. We also list video games, though at present, we do not list commercials, video clips or music videos (these go to the biographical section under 'other works'). General public interest is assumed if a work has been:
Released in cinemas.
Shown on non-local TV.
Released on video or prints have been made available to the public (See exceptions below on limited distribution titles).
Listed in the catalog of an established video retailer; (e.g. Amazon.com).
Accepted and shown on film festivals that don't accept everything regardless of its quality (if you have doubt, see this page for details).
Made by a (now) famous artist or person of public interest.
Made famous for some reason and is widely talked about/referenced in non-local media or the 'film community' or is now of general historic interest for some reason.
NOTE: Unless general public interest is assumed for one of the reasons stated above, general public interest is NOT given just because a work has been:
Digitized and put on an internet page for downloading (). For more information, please see this special guide.
Offered to the public on the web via home made video tape/DVD-R copies.
Made during/for a film class, workshop or any other educational program.
Made for a local institution (such as a university or company) for internal use.
Made for private home use only (i.e. like a home movie, which is of a strictly private nature).
Made for local consumption by friends, family members and neighbours, the local school campus etc. (including "local access television").
IMDb retains the right to reject any work whose eligibility according to above rules is dubious and/or unverifiable. This may include works which are in their very first development stages. If you would like to submit a project in development, please sign-up for IMDbPro. IMDb retains the right to change and adapt eligibility rules as circumstances require.NOTE: While individual TV series episodes are accepted, they should not be submitted using the new title form; instead, you should use the "Add Episode" button associated with the series title.