SpaceX Chief Engineer Elon Musk takes part in a joint news conference with T-Mobile CEO Mike Sievert (not pictured) at the SpaceX Starbase, in Brownsville, Texas, U.S., August 25, 2022.Adrees Latif | ReutersElon Musk has announced big, albeit confusing, plans for Twitter since he took over the social network last month.Musk wants to vastly increase the revenue the company makes through subscriptions while opening up the site to more “free speech,” which in some cases seems to mean restoring previously banned accounts like the one owned by former president Donald Trump.But Musk’s plans for Twitter could put it in conflict with two of the biggest tech companies: Apple and Google.Tensions are brewingOne of the biggest risks to Musk’s vision for “Twitter 2.0″ is the possibility that his changes violate Apple or Google’s app rules in a way that slows down the company or even gets its software booted from app stores.Tensions are already brewing. Musk complained in a tweet just last week about app store fees that Google and Apple charge companies like Twitter.”App store fees are obviously too high due to the iOS/Android duopoly,” Musk tweeted. “It is a hidden 30% tax on the Internet.” In a follow-up post, he tagged the Department of Justice’s antitrust division, which is reportedly investigating app store rules.His complaint is over the 15% to 30% cut Apple and Google take from purchases made inside apps, which could eat into the desperately-needed revenue from Musk’s plans for $8 per month from Twitter Blue subscriptions.Over the weekend, Phil Schiller, the former head Apple marketing executive who still oversees the App Store, apparently deleted his widely-followed Twitter account with hundreds of thousands of followers.Phil Schiller, senior vice president of worldwide marketing at Apple Inc., speaks at an Apple event at the Steve Jobs Theater at Apple Park on September 12, 2018 in Cupertino, California.Justin Sullivan | Getty ImagesThere are signs Twitter has already seen an increase in harmful content since Musk has taken over, putting the company’s apps at risk. In October, shortly after Musk became “chief Twit,” a wave of online trolls and bigots flooded the site with hate speech and racist epithets.The trolls organized on 4chan, then barreled into Twitter with anti-Black and Jewish epithets. Twitter suspended many of the accounts, according to the nonprofit Network Contagion Research Institute.Musk’s plan to offer paid blue verification badges have also led to chaos and accounts impersonating major corporations and figures, which have caused some advertisers to shy away from the social network, in particular, Eli Lilly after a fake verified tweet erroneously said insulin would be provided for free.The app stores noticed.”And as I departed the company, the calls from the app review teams had already begun,” former Twitter head of trust and safety Yoel Roth wrote this month in the New York Times.Fees and subscription revenueTwitter and Apple have been partners for years. In 2011, Apple deeply integrated tweets into its iOS operating system. Tweets that function as official company communications are regularly posted under Apple CEO Tim Cook’s account. Apple has advertised new iPhones and its big launch events on Twitter.But the relationship appears poised to change as Musk moves to generate a larger bulk of income from subscriptions.Twitter reported $5.08 billion in revenue in 2021. If half of that comes from subscriptions in the future, as Musk has said is the goal, hundreds of millions of dollars would end up going to Apple and Google — a small amount for them, but a potentially massive hit for Twitter.One of Apple’s main rules is that digital content — game coins, or an avatar’s outfit, or a premium subscription— that’s purchased inside an iPhone app, has to use Apple’s in-app purchasing mechanism, in which Apple bills the user directly. Apple takes 30% of sales, decreasing to 15% after a year for subscriptions, and pays the remainder to the developer.Companies such as Epic Games, Spotify, and Match Group lobby against Apple and Google’s rules as part of the Coalition for App Fairness. Microsoft and Meta have also filed briefs in court criticizing the system and made public remarks aimed at app stores.One option for Musk is to take an approach similar to what Spotify has done: Offer a lower $9.99 price on the web, where it doesn’t pay Apple a cut, and then users simply log in to their existing account inside the app. Users subscribing to a Premium subscription inside the iPhone app pay $12.99, effectively covering Apple’s fees.Or Twitter could go further, like Netflix, which stopped offering subscriptions through Apple entirely in 2018.Musk could sell Twitter Blue on the company’s website at a cheaper price and tweet to his over 118 million followers that Blue is only available on Twitter.com. It might work and could help cut Apple out of any fees.But that also means Twitter would have to remove many options for informing users about the subscription inside the app, where they’re most likely to make a purchasing decision. And Apple has detailed rules about what apps can link to when telling users about alternative ways to pay.As Netflix’s app says: “You can’t sign up for Netflix in the app. We know it’s a hassle.”A power struggle over content moderationTim Cook, chief executive officer of Apple Inc., speaks during the Apple Worldwide Developers Conference (WWDC) in San Jose, California, U.S., on Monday, June 4, 2018. David Paul Morris | Bloomberg | Getty ImagesMusk faces the power of Apple and Google and their ability to decline to approve or even pull apps that violate their rules over content moderation and harmful content.It’s happened before. Apple said in a letter to Congress last year that it had removed over 30,000 apps from its store over objectionable content in 2020.If app store-related problems strike Twitter, it could be “catastrophic,” according to the former Twitter head of trust and safety Roth. Twitter lists app review as a risk factor in filings with the SEC, he noted.Apple and Google can remove apps for various reasons, like issues with an app’s security and whether it complies with the platform billing rules. And app reviews can delay release schedules and cause havoc whenever Musk wants to launch new features.In the past few years, the app stores have started more closely scrutinizing user-generated content that starts shading into violent speech or social networks that lack content moderation.There’s precedent for a complete ban. Apple and Google banned Parler, a much smaller and conservative-leaning site, in 2020 after posts on the site promoted the U.S. Capitol riot on Jan. 6 and included calls for violence. In Apple’s case, the decision to ban high-profile apps is made by a group called the Executive Review Board, which is led by Schiller — the Apple executive who deleted his Twitter account over the weekend.Although Apple approved Truth Social, Trump’s social networking app, in February, it took longer for Google Play to approve it. The company told CNBC in August that the social network lacked “effective systems for moderating user-generated content” and therefore violated Google’s Play Store terms of service. Google eventually approved the app in October, saying that apps need to “remove objectionable posts such as those that incite violence.”Musk reportedly fired many of Twitter’s contact content moderators this month.Apple and Google have been careful while banning apps like Parler, pointing to specific guideline violations like screenshots of the offending posts, instead of citing broad political reasons or pressure from lawmakers. On a social network as large as Twitter, it’s often possible to find content that hasn’t been flagged yet.Still, Apple and Google are unlikely to want to wade into a difficult battle over what constitutes harmful information and what doesn’t. That could end up inviting public scrutiny and political debate. It’s possible that app stores simply delay approving new versions instead of threatening to remove apps entirely.Future features could also irk Apple and Google and prompt a closer look at the platform’s current operations.Musk has reportedly talked about allowing users to paywall user-generated videos — something that former employees think would lead to the feature being used for adult content, according to the Washington Post.Apple’s App Store has never allowed pornography, a policy that dates back to the company’s founder, Steve Jobs, and Google also bans apps centered around sexual content.Anything that isn’t safe for work needs to be hidden by default. Twitter currently allows adult content, which could put it even more directly into reviewer sights.”Apps with user-generated content or services that end up being used primarily for pornographic content … do not belong on the App Store and may be removed without notice,” Apple’s guidelines say.But Musk often runs towards battles, not away from them. Now he has to decide whether it’s worth taking on two of the most valuable and powerful companies in Silicon Valley over 30% fees and Twitter’s ability to host edgy tweets.An Apple representative didn’t respond to a request for comment. A Google representative declined to comment. Twitter didn’t respond to an email and the company no longer has a communications department. Musk didn’t respond to a tweet.