I'm probably the last person on the planet to notice this, but the Ophis assembler is out in version 2.0 at http://michaelcmartin.github.io/Ophis/ . Note that our Resources entry at http://6502.org/tools/asm/ still points to 1.0. At a first glance, the manual also seems to have been updated as well, with a bunch tutorial stuff.

For those who haven't tried it, Ophis is pure Python assembler with a slightly different syntax. From the Preface of the manual:

Ophis's syntax is noticably different from the formats traditionally used for these chips; it draws its syntactic inspiration primarily from the assemblers for more modern chips, where the role of tokens is determined more by what they're made of and their grammatical location on a line rather than their absolute position on a line. It also borrows the sophisticated methods of tracking the location of labels when writing relinkable code—Ophis expects that the final output it produces will have only a vague resemblance to the memory image when loaded.

I picked Ophis because it runs great regardless of platform (I have moments where I am annoyed enough at Apple to want to switch back to Linux, and this wouldn't be a problem) and supports the 65c02 features. Then again, I had the advantage (if that is what you want to call it) of stating from scratch with my code. Works fine for me, for what it is worth.

Well noted - I've updated the link.
Thanks
Ed