There will always be a market for entertainers to produce live performances and bespoke works, and that market doesn't require DRM because the product is intrinsically uncopyable.
Likewise, source code is just data. You can't really sell source code. You have to find something else, something intrinsically uncopyable, and sell that instead.
Not quite. You can sell digital data, you just have to accept that there's only ever one "copy" for sale. Adjust the price accordingly.