There has been quite a bit of 2nd and 3rd hand information flying around over the last couple of days about Rockstar Games coming down hard on any users with modified versions of GTA V (primarily mentioning PC version but obviously applying to the console versions which have been modified too).

The rumour: Online bans for Story Mode modifications.

A few quoted sources I have seen:

So, the EULA has been changed to align with what I would term a "standard no-reverse-engineering" clause.

This isn't something we're likely to see an official Newswire announcement about, although there have been a couple in the last 18 months to announce their crack-downs on on-line modders.

I've never been heavily into modding my games. I have a few modded installs of GTA San Andreas but they are mostly visual mods (vehicle models, texture replacements, some handling and language file updates etc). It was certainly a long time after I had completed the game a couple of times before I applied any modifications at all.

I have never modded GTA IV and had no intention of modding GTA V.

Rockstar do not have the same history of embracing the mod community that say Bethesda (Elder Scrolls) or Valve (Counter Strike etc) do. There has never been any official suggestion that they would actively encourage mods the same way Bethesda did with the Steam Workshop for Skyrim, for example.

As a victim of early PS3 online modders ($192 million in unwanted shared cash distributed to all lobby players that still to this day has screwed up my main player stats on PS3 which also migrated to PS4 and PC), I support 100% any crack-down on modders in public lobbies GTA Online.

That said, banning players from Online due to detection of Story Mode only modifications does concern me in a "what I do with the software in the privacy of my own home" kind of way. It makes me think there is much less of a disconnect between the two modes than Rockstar would have us believe and anything that can be modded in Story Mode could potentially have impact in Online. This is not altogether a surprise to me, since we have seen mods and glitches to get so-called "exclusive" content from online to Story mode and vice versa.

I personally doubt that the Online bans are solely for having Story Mode mods. I would think that that is an easy red flag to alert the Rockstar support team to investigate the account fully and if there are any Online discrepancies found, only then would the ban hammer fall.

UPDATE 1 day later

The OFFICIAL response to the rumours, confirms my final paragraph conclusion.

"I’m having soo much fun with GTAV on the PC but I just have one question about it, how come you are not allowing mods for it?”"
— @ClarkMatthew63
"“Will I get banned from GTA Online for using a FoV Mod or Oculus Rift mod?”"
— @Mattophobia
"We have always appreciated the creative efforts of the PC modding community and we still fondly remember the awesome zombie invasion mod and original GTA map mod for GTAIV PC among many other classics. To be clear, the modding policy in our license has not changed and is the same as for GTAIV. Recent updates to GTAV PC had an unintended effect of making unplayable certain single player modifications. This was not intentional, no one has been banned for using single player modifications, and you should not worry about being banned or being relegated to the cheater pool just for using single player PC mods. Our primary focus is on protecting GTA Online against modifications that could give players an unfair advantage, disrupt gameplay, or cause griefing. It also bears mentioning that because game mods are by definition unauthorized, they may be broken by technical updates, cause instability, or affect your game in other unforeseen ways."
Rockstar Games