Could it be that they are publishers AND distributors? Like Sega. Sega have published some games on the Amiga, while they have also licensed out some of their arcade titles to other companies (Elite, US Gold, Mindscape, etc.)
Another example is Krisalis, who have published several titles, but have also developed games that were released by different publishers (example: Passing Shot - a Sega coin-op, Krisalis programmed it, Mirrorsoft/Image Works published it). Teque Soft are credited as the developers, but the Krisalis page reads differently.
Which reminds me, their site seems to have disappeared. It used to be here
, but seems to be gone.