Ambitious GTA mod Liberty City Preservation Project has been shut down, but contrary to what you might think, the mod's developer insists that the takedown wasn't due to a DMCA request on Rockstar's part.
In a message shared to the mod's Discord server (via GameRoll on X), modder nkjellman says that the choice to take the mod down was made "due to the unexpected attention" the project received, and that a decision was reached "after speaking with Rockstar Games".
However, in a followup message, nkjellman clarifies that the takedown "isn't a DMCA" but rather "a friendly takedown, mutually agreed upon by all parties involved". The modder says there's "no negativity between [their team] and Rockstar Games / Take-Two Interactive".

The modder goes on to say that you shouldn't download LCPP from unofficial sources because they "may contain malware", and that users also shouldn't share download links in the Discord server.
Of course, although nkjellman says the takedown was "friendly" and that Rockstar didn't issue a DMCA, that doesn't mean it wasn't Rockstar who unofficially requested the mod's removal.
It's very possible that if nkjellman and their team had refused to take down LCPP, a DMCA would have been the next step, so even though a DMCA wasn't issued, it could well have been the threat of a DMCA that caused the modders to take down the project.
Whatever the case may be, one thing's for certain: you won't be able to get Liberty City Preservation Project from official sources anymore, so I hope you've already got the mod downloaded if you want to keep playing it.

If you're wondering exactly what the Liberty City Preservation Project mod was, it was an ambitious attempt to essentially mod the entirety of Grand Theft Auto 4 into the GTA 5 engine, complete with the whole Liberty City map to explore.
In a way, it's not surprising that it's been taken down. Rockstar's parent company Take-Two is notoriously hostile towards modders, having taken down several GTA-related modding projects in the past.