Ok so it looks like microb-engine_20091230-1.9.2.orig.tar.gz in the SDK repos came from some version of the mozilla-central tree (which version it is I cant seem to find) and then microb-engine_20091230-1.9.2-6.8+0m5.diff.gz sits on top of it to add debian packaging (including what looks like a bunch of local patches)

https://bugzilla.mozilla.org/show_bug.cgi?id=906072 indicates that the maemo bits that were in Gecko were removed from Gecko a while back.

Seems like getting newest Gecko to be usable on Maemo might not be so easy, we need to figure out just what bits were removed (in bug 906072 and any number of other bugs) that Maemo was using and which of those bits are actually important and also figure out which of the local patches in the .diff.gz file are actually important.

If the goal was "lets build an alternative browser for Fremantle" we could just get any browser that built and ran on the platform and make it work (e.g. fixing up qmlbrowser to make it go). But the goal isn't that, the goal (at least my goal) is to find a way to make a newer gecko rendering engine function as the system browser on Fremantle (with the same level of system integration as the current one) so we get the advantage of all the security fixes, technology support and other things that come with a new browser but also have the system integration that comes with the current browser engine.

That said with all the bugs that reference removing Maemo-specific stuff (bug 1080529, bug 906072, bug 653201 and likely others), the work required to make anything resembling a recent Gecko to actually be usable (let alone feature complete) on a Fremantle installation may be far more than the few Maemo developers left in the community can handle. And that's before you start thinking about gtkmozembed and what to do about it.