The Japanese Language Tools dictionaries are actually just documents in a standard Japanese dictionary and eBook format called EPWING. You can use them on any device as long as it lets you enter and display Japanese and has an EPWING reader program. I've personally used my dictionaries on Windows Mobile PDAs and phones (quite a few different models), Palm OS PDAs (ditto), Windows XP (desktop, notebook, and tablet), and the iPod Touch (works the same as iPhone and iPad). I've also tried out the Japanese input system in Android. I can give you some starters for those platforms; for the rest, you'll have to turn to the net for resources and instructions. As always, I recommend trying out some of my free dictionaries before buying a dictionary from me or anyone else.
Windows XP. Simply activate East Asian Language support and a Japanese IME from the control panel, if you haven't already, then install the excellent (and free!) program EBWin (scroll down to the middle of the page). One cool feature most people don't use: the IME pad. Using the mouse or, if you have it, a touchscreen or tablet, you can draw kanji in to enter them just like in the Windows Mobile systems I sell. Some tiny subnotebooks now come with touchscreens, making this feature even easier to use. I've got a Viliv X70EX tablet I just love for when I'm on the road--I admit, though, that I use a roll-up rubber USB keyboard instead of the onscreen virtual keyboard whenever I'm going to be typing more than a short note. I deliberately chose the XP version rather than the one with Windows 7 Starter for the reason mentioned below.
Windows Vista and Windows 7. Annoyingly, the excellent language support included for no extra cost in all versions of XP now comes only with Ultimate and better versions of Vista and 7 (though you can pay Microsoft extra to add it to lesser versions). However, folks online are reporting that you can install the Google Japanese IME onto the cheaper versions of Vista and 7--you should do some research online onto installing it onto your particular version of Vista or 7, though, because I haven't tried it myself and can't offer any guarantees (I welcome any information users can give me to pass along here, though). Google IME looks and works almost exactly the Japanese support that comes with XP, including the IME pad for handwriting entry (though the dictionary it uses is smaller, meaning it happens a bit more frequently that when you enter hiragana with the keyboard and hit the "convert to kanji" button, the word you're trying to enter doesn't appear--you then have to enter the word one kanji at a time). If you have Vista or 7, you can install Google IME and check it quite easily. Once you've got Japanese going, install EBWin as with XP and you're good to go!
Mac OS X. OS X includes excellent Japanese support. As with XP, you just have to enable it from the settings. There are a few different choices for EPWING programs. The best is EBMac, from the maker of the EBPocket program used in JLT Complete Systems and on the iPhone. It's optimized for EPWING, so it's fast and efficient, it offers the complex search options that make EBPocket and EBWin so powerful, and it's compatible with the .ebz compressed EPWING format of the JLT dictionaries. Plus, it's free. It's a new program, so check back frequently for updates, a manual, and maybe an English-interface version if the current installer doesn't offer one. If you want to try something else, I don't know if all of the other Mac dictionary programs are compatible with the .ebz compressed EPWING format--if one doesn't work, try another. Here are a few I've found (but haven't tried): Kamonos (still available?), Kotonoko, Logophile (not free), and JEDict. There may be more.
Linux. I've seen enough to know it's out there, but you'll have to google it yourself. I don't know much about Linux.
Nokia Internet Tablets/Maemo. Ditto. It's there--but you'll have to go get it. I don't know how good the Japanese support is--whether there's handwriting entry or just a keyboard IME, and how well those systems work. My impression from what I saw a while ago is that Japanese support is fairly simple--limited keyboard IME. But there may be something better available now. Again, please check it out yourself before buying anything--my knowledge here is too shaky to base any decisions on.
Android. I've tried out the built-in and freely installable Japanese support on Android myself. While it's easy to enable or add free Japanese support, the problem is that it's still really primitive. Only a keyboard (real or virtual) IME, and it's based on a very small dictionary--when I entered even some fairly common words in hiragana, the IME couldn't convert them to kanji. However, ATOK has recently released an Android version of its excellent IME. It includes a good virtual keyboard IME (also works with physical keyboards, either built-in or accessory) and a phone keypad-style IME. Unfortunately, it doesn't include the excellent handwriting recognition that its versions for regular Windows computers and old Windows Mobile computers included. As I write, ATOK for Android is 980 yen. With that and the excellent EB Pocket Pro app for using EPWING dictionaries now also available for Android (600 yen for the pro version; definitely worth the upgrade from the free one), Android users will be able to use the JLT as well as iPhone and iPad users can--excellent except for the lack of any convenient way to enter unknown kanji.
There's still no good japanese handwriting entry for Android (a couple of apps out there, but so bad as to be useless). The difficulty is that making a good IME requires huge databases, and all the good ones were made by and belong to large companies (available free and open ones, like the developing Social IME used in some IMEs for Android, are still pretty much useless). That's why Microsoft can build excellent IMEs into the Japanese versions of its mobile operating systems (which enterprising hackers can port to the English versions of the Windows Mobile OS), and why Apple could include a good keyboard IME in the iPhone. And it's why a free OS like Android can't include even a decent keyboard IME in the OS, and why small developers can't come out with reasonably priced keyboard or handwriting IMEs for it. It takes a big player like ATOK to do it, and since they've decided not to include a handwriting IME, I don't think there's much chance of a decent one coming out anytime soon. As with the iPhone and iPad, most Android devices use a capacitive touch screen--this type works well with big fat fingertips and allows multi-touch gestures (and so it's clearly the best choice for what 99.99% of users want to do with their phons and tablets), but it doesn't work with a fine stylus and lacks the precision needed for handwriting recognition of complex characters to work well (and, on pocketable devices, the screen is really too small to let you draw a complicated kanji with your fingertip--try the Chinese handwriting recognition on a friend's iPhone to see what I mean--while it's a miracle that it works sometimes, it's a pain in the neck compared to using a stylus on a resistive touchscreen). That may be why ATOK and the other big companies aren't bothering to release handwriting IMEs for the Android OS--perhaps they'll revisit that decision once Android tablets, with enough screen space for really big handwriting input areas, really start to proliferate.
. I'd love for someone to prove me wrong and point me to an excellent Android handwriting IME available now--putting the whole JLT system on an app that can be downloaded and installed onto an Android handheld or tablet would let JLT get out of the hardware business and make my life much simpler (and open up much larger markets to me). That's why I've got a couple of Android devices and an emulator and keep trying everything that comes along.