That's the portability bit the presenter mentions, and is a very important concern in practice. But how about recompression? For example many PNG files are suboptimally compressed partly because PNG is an old format and also because many softwares have been too dumb to produce a well-optimized PNG. In that case we may benefit from a transparent recompression, which may be done either by using a better library like libdeflate or by internally using a separate format that can be quickly transformed from and back to PNG. In fact Dropbox did so for JPEG files [1]. When I'm saying "so much better" I was thinking about such opportunities that benefit end users.
Dropbox apparently still uses Lepton or any successor internally, but the open source version is abandoned because it posed larger maintenance burden than internal projects.
Has Dropbox said this anywhere? Or are you assuming it based on something like "this kind of project is very easy to maintain internally so there's no reason why they would have stopped using it"?
At least at the time of abandonment, Dropbox did say (emphasis mine):
> While we did ensure that the reported vulnerabilities don’t affect our internal use of Lepton, we unfortunately don’t have the capacity to properly fix these and future issues in this public repo.
As far as I know this is indeed the last known public mention of its use, but given that Lepton was already in use and dropping it would substantially increase its traffic, it is reasonable to assume that its use somehow continues to this day.
That's pretty strange. If they're using it in a meaningful way, then they're applying it to arbitrary files, so they'd generally need fixes for almost all the bugs. So what resources would be lacking so badly that they give up on releasing?
It could just be a lame excuse. Open sourcing with zero support would be better than not doing it. But I imagine that this seems valuable enough to keep secret, or at least not to pay money to polish up for external use.
[1] https://github.com/dropbox/lepton