By switching to the GPL, we’re reaffirming our commitment to the free software world. One big reason for this decision was to reduce the lead time between bugs being fixed in the development tree and users seeing the fixes, especially those users dependent on Linux distributions.
This seems notable, as for years Ghostscript has served as the usual example of the free the future, sell the present open source business model. Previous GPL releases were about one year/one version behind AFPL (which restricts commercial use) releases.
Ghostscript is also notable for having a long running bug bounty program.
Addendum 20060608: The quote above doesn’t address the business reasons for making the current codebase GPL. Perhaps all paying customers are unwilling to release under GPL. If so Artifex would lose no commercial licensing revenue and gain some goodwill and outside contributions and reduce the amount of effort required to do releases of year or more old code.