Remaining issues include Amazon Music failing to advance tracks in playlists (the JIT has been exonerated, so I'm still spinning my wheels here), disabling the last remnants of signed extensions (which I philosophically disagree with) and changing the update notification source. Otherwise it seems to function very well once it's loaded everything and got most of the browser chrome in the JIT. The browser is tested on my usual lab machines, the 16GB monster Quad G5, a 1.5GB 1.33GHz iBook G4, a 1.25GB 1GHz iMac G4 15" and a 2GB 450MHz Sawtooth G4, all running Tiger. TenFourFoxBox appears to work with no changes needed but you may want to keep 38.10 around for right now if you are using foxboxes heavily, just in case (please report issues as you find them).
On the build side, pretty much the process is the same as 38 except that gcc 4.8 is now required. The MacPorts build of gcc is what I use, and I'd like to hear if other builds from our other unofficial package maintainers also work. The hacked strip7 unfortunately is still needed for stripping release binaries to handle the variant N_SECTs in the object files. One irregularity is that gcc 4.8 can't distinguish Objective-C messages from C++11 lambdas, or rather, that Objective-C++ has priority over lambdas, so that you can't reliably use both language features in the same file. This occurs in exactly one place in the entire code base, in code we don't support anyway, so it's #ifdefed off. If your local changes run afoul of this, try adding #define GCC_SUCKS_MOOSE_WANG (yes, really, I was a bit peeved that day) and see if it builds with that, or put the C++11 lambdas into another file and have your Objective-C++ call it instead. The build instructions are updated and available now, and with luck our esteemed colleague in the Land of the Rising Sun will be able to build Tenfourbird on the 45 base as well. Also, as you will see, the G3 version built just fine and will still be supported in 45 and thereafter.
Localizers should be aware of two new files, TenFourFox.dtd and TenFourFox.properties, which will be the locale basis for features I am considering or planning to release. I'd rather have translations for features I decide against implementing than not having strings for features I do implement, so almost nothing in those two files (which are roughly the same strings in different places) is being used right this second; that said, however, the idea is to roll out features using these strings during 45's lifetime as we move from source parity to feature parity and this will enable me to do so more quickly. If you would like to contribute to the localization effort (we really appreciate it), Chris T wrangles the cats in issue 42. The aim is to have substantially the same languages available for 38 available for 45 at or near the time of release in about six weeks. Your help is invaluable in this effort.
Finally, let's give 38 a rousing round of applause for being a solid, long lived branch release as it rides off into the ESR sunset. Its end also means the end of one of the oddest chapters in Firefox history, Debian Iceweasel, which has now reverted to being "just" Firefox as of 45ESR. Although both we and they rebranded ourselves because of various changes to Firefox we were making, we'll still be keeping our name because we really do change the feature set and make various platform-specific changes Mozilla would probably find unacceptable otherwise. Plus it gives you guys something to still complain about, along with the icon. :)
Don't file Github tickets on beta issues; post them in the comments. Please be kind. This was literally months of work. Thanks and let's start banging the bugs out.