Does a hacked ROM qualify as an actual ROM? I could easily link a patched version if that was allowed, but I kinda doubt it. :p Anyways, the version you mentioned, e.g. the easily-found-reddit thread, will likely turn up a v1.2 or v1.3 version of the hack. It's probably for the best to hunt down a clean vanilla Crystal .gbc and then apply the v2.0b patch.
Otherwise, folks can just go
(you need an account to see links) if they have a 2DS/3DS with custom firmware. The .cia download there acts like any other .cia file, easily installable as a stand-alone application on the 2/3DS with any .cia installer (FBI, BigBlueBox etc).
Crystal Clear is a great hack though, 10/10 would definitely recommend as a Gen 2 experience. The open world is fantastic, the restored Kanto areas make it seem like an actual region again, and the soundtrack legit surprised me at times with its custom stuff. It allows for a lot of neat Pokemon to be obtained easily so you can craft whatever kind of team you please: my starter was a Porygon, and two of the first additions to my team were a Larvitar and an Omanyte, for example. I never trained a Pokemon that learned Fly, but it was still incredibly easy to get around with Surf, the ingame ferry system and the trains.
I haven't properly finished my playthrough yet, but I have completed my Pokedex in full on it! You mentioned that other legit games can communicate with it-- one thing I've found is that if you slot it into an N64 emulator with the Transfer Pak options properly filled out, Crystal Clear can also communicate with Pokemon Stadium 2! The interactions are clean and safe, you can easily store or use Pokemon on Stadium 2 as well as get its daily Mystery Gift function.
Even better, though, is that
Poketransfer and Pokebank identify Crystal Clear as legitimate. So if you install the .cia on your hacked 3DS/2DS, you can actually migrate your Pokemon from this game to your gen6/7 game. The only "illegitimate" thing about any of the Pokemon in Crystal Clear is that they're often found in different areas than in vanilla Crystal, and Poketransfer doesn't actually pay attention to that bit of data.
You can even migrate the Celebi and Mew -- the Celebi fits legitimate parameters, while the Mew can be fixed to be legit by an ingame NPC. It's pretty great.
(That being said, if anyone
without a hacked 3DS/2DS wants me to pop open their Crystal Clear save file and help transfer their Pokemon to their real-world gen6/7 games, just send me a PM. I can help with that kind of stuff.
)
edit #234234: (you need an account to see links), for anyone who's played the game so far and is interested in what new content there is!