The same is true if we had maybe 10,000 Zelda games on the market. Imagining that is kind of weird. But the result is just awesome.
First of all even if copyright was expired it doesn't mean access to source code.
Secondly, do you really think that having access to 20 year old version of Photoshop (source code or not) would be significant factor for anybody to enter the market? Making it work on modern systems would mean essentially a complete rewrite, at which point the original copyright would be irrelevant. Making it competitive would be probably more difficult with the original codebase than with a new clean design.
Maybe it should. Registering a copyright already requires the submission of several copies of the work. Why shouldn't the source code necessary to produce that work be a required part of the submission? If the public is to be expected to take advantage of public domain works, they must have access to high quality versions in useful formats.
http://en.wikipedia.org/wiki/Copyright_registration
> Registration is still required in the US for some benefits, such as awards of statutory damages
When is my work protected? Your work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device.
Do I have to register with your office to be protected? No. In general, registration is voluntary. Copyright exists from the moment the work is created. You will have to register, however, if you wish to bring a lawsuit for infringement of a U.S. work. See Circular 1, Copyright Basics, section “Copyright Registration.”
If I create a story it is automatically copyrighted (unless I specifically license it differently) however if I wanna sue, my copyright must be registered.