They could put the code on GitHub, allowing contributions, with a license that turns into BSD or MIT after two years, and with the caveat that you can only run the (new) code if you purchase a license key first.
In companies of reasonable size, the deterent against piracy is the existence of a license itself, the actual copy protection and its strength aren't as important. The reason those companies (mostly) don't crack software isn't that the software is hard to crack, it's that their lawyers wouldn't let them.
Sure, this would make Zed somewhat easier to crack, but I think the subset of users who wouldn't use a Zed crack if Zed was binary-only but would use one if there was source code available is very small.