Hi. I'm quite sure a bug like this should exist already, but I couldn't find it. I believe a considerable part of Seamonkey users are developers, and we're not doing much for them. So I was thinking... why don't we integrate the new Firefox developers tools into Seamonkey, too? I've been using them for a while and they're great. Since Firebug is not compatible with Seamonkey anymore, I believe it would be a great help for developers. Is there any technical reason why we can't integrate them?
A lot of code lives in browser/ and relies on browser UI and components. Things have improved with some of the recent changes we've been doing. Nonetheless, there's still a lot of work to make the entire set of devtools to work with Seamonkey. It might be easier to start off with one tool at a time. For example the Web Console and the JS Debugger have a lot of code in toolkit, and the UI is fairly self-contained. In the Web Console's case HUDService.jsm is the Firefox UI glue-layer. If you replace HUDService with a Seamonkey-specific implementation and other small bits, one should be able to get the Web Console working with Seamonkey. The webconsole.xul and webconsole.js files should be much safer - albeit they are not 100% "clean". There's also bug 768103. For the debugger the story might be similar, but I do not know the UI code very well.
After almost a year, are there any news on the feasibility of this implementation?
Edmund was looking into this in Bug 574955 (Make webconsole work in SeaMonkey) but it was a moving target and back then a lot of code was hard coded for firefox. Bug 768103 should certainly help matters.
Note that Firebug (inofficially) allows to be installed on SeaMonkey until now and people are obviously using it. As the upcoming Firebug 3 will be based on the DevTools, there won't be any support for it anymore as long as the DevTools are not included in SeaMonkey. Sebastian  https://groups.google.com/forum/#!msg/firebug/9nWmTvZv6lw/d_pkNjo1QBgJ