Recursion error was due to an ancient version of MooTools used by the copy of JxLib we had in the Fusion repo. Couldn't determine the full provenance of the bundled JxLib (especially how our checked in copy was "built"), so I surgically grafted in the latest 1.2.x version of MooTools into our jxlib.uncompressed.js which fixes the recursion error.
We really shouldn't be keeping "compiled" third party libs for Fusion if there's no documentation detailing how the library was built.
This RFC fixes that for OpenLayers at least. Rebuilding OpenLayers.js is just overlaying our custom modifications (which we now keep track of) on top of the standard OL 2.12 source tree and build a new copy from that.