Hmm? The stack buffer in yxml will never cause parsing to block, and there's no added dependencies on... anything? I don't think that buffer causes any problems even on a size-restricted microcontroller that doesn't have malloc(). As long as you can find ~512 bytes or so of free memory you can parse a lot of files.
The only situation in which that buffer would cause an error is when the application used a too small buffer, or when the document is far too deeply nested or has extremely long element/property names. Both the maximum nesting level name lengths should, IMO, be limited in the parser in order to protect against malicious documents. Most parsers have separate settings for that, yxml simplifies that by letting the application control the size of a buffer.
The stack buffer in yxml is also used to make the API a bit easier to use. With the buffer I can pass element/property names as a single zero-terminated C string to the application, without it I would have to use the same mechanism as used for attribute values and element contents, and that mechanism isn't all that easy to use. (This is the one case where I chose convenience over simplicity, but I kinda wanted the validation anyway so that wasn't really a problem)
