It’s available in PDF form from here, courtesy of the German Research Foundation. This journal contains quite a bit of patristic-related material. This is because the editor, Bernd Manuwald, applied to that foundation for a grant to do it. Well done Dr Manuwald!
I understand that he is also applying for money to digitise the remaining issues. Frankly he looks like a hero to me.
The last three years are not available online. This protects the subscription income from universities, where the very latest articles are needed. But it is a mark of Bernd Manuwald’s vision that he has limited the offline material to just that range.
None of us ordinary mortals will care that the last three years are not freely available. It is rarely a matter of concern to the interested amateur to keep up with the very latest papers. But the audience for a century of material is wide.
Later: Adrian Murdoch at the ever-excellent Bread and Circuses blog has picked up the story, and tells us that ZPE is also available freely online, although I can’t actually find it on that site. Come on gents at the ZPE: if you’ve done the work, make it obvious where it is!