It's not illegal, at least not in the US.
It might be civilly actionable by certain software authors, depending on what other code Colby depends on for EcuFlash, but he appears to have been very careful in that regard. Qt would have probably been the only one that was a possible issue, and since they switched to the LGPL recently, it's a moot point. (Back in the day, he would have needed a commercial license to distribute source-free.) One other thing that jumps out at me is the graphing; it looks like gnuplot output, which has some, er, "very odd" redistribution restrictions. I'm guessing it's just using one of the several Qt interfaces to gnuplot, but without source it's tough to say.
Regardless, as long as some portion of the mix isn't GPL-licensed (like gnuplot-cpp), there's nothing much to complain about here.
Anyway, if you were to obtain a copy of the source code for EcuFlash by some means, you could reasonably take
this licensing page to mean that you have the redistribution rights that the GPL provides. As a version is not specified, you'd have to make an educated guess as to which version applies here; the last updated date on that page is 2006, so it would be reasonable to assume that GPL v2 was implied.
I've been told that Colby will make the source available to select folks upon request (in fact, the RomRaider development community
had access to it back in
at least 2007), but this kind of limited distribution is hardly what everyone was expecting; we were basically lied to
several years ago (the whole thread is worth reading). I appreciate what availability of EcuFlash has made possible, but we're still building on the back of a software package we can't inspect, modify, or improve. Which, aside from the price (which is free only if you don't consider the cost of the cables and adapters), isn't a much better situation than the commercial products available on the market.
As a pointer in the right direction if you really want to work on this stuff (as opposed to simply wanting access to the source as a matter of principal, which I can certainly appreciate), an
early version of Colby's HC16 kernel (0.91) is bundled with the
EcuExplorer source; it doesn't get you SH reflashing (so no newer STi ECUs, no Evos), and it's a binary blob (so you'll want to pull out IDA), but it's a place to start. Colby has known that's been there for a very long time, and I've seen no assertion on his part that it's covered by anything but the GPL above, but you'll want to consider licensing carefully before spending too much time with it. ("Inevitable disclosure" can be annoying.)
(On an unrelated note, I noticed Hamish added flashing capabilities to EvoScan recently; I wonder if he independently developed that, or if the flashing kernel was borrowed from EcuFlash? I haven't looked to see if HC16 flashing was included as well, but I think he's focused on the Evo stuff anyway, hence SuperH. Regardless, it's still a closed-source product, but interesting just the same.)