After days of technical issues, Vero says app will be free 'until further notice'

Vero, the Instagram-like app that suddenly went viral in the last couple days, has more than a million users, but it's still free -- at least for now.

The app doesn't host any ads, and the company's founders have always said they intend to charge users a yearly subscription to support the business. The fee was originally supposed to kick in after the app's first million users signed up (this first wave of users would be exempt from the fee).

But with the app getting so much attention that it's been almost unusable for days, Vero now says the app will remain free "until further notice."

"Due to the large wave of new users joining over the past several days, we have encountered technical issues which have left many experiencing service interruptions," the company writes on its website.

"As promised, our first million users have access to Vero free for life. However, given the service interruptions, we are extending that offer to all new users until further notice."

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The company didn't say when the subscription will start to kick in or how much it will cost, but said it would announce subscription details "soon." Vero founder Ayman Hariri told CNBC last year the fee would be "a few dollars a year."

Assuming Vero keeps its word that the first million signups will be exempt from paying any fees, that could still add up to a lot of money for the startup. Vero, which has been the top app in the App Store for three days now, has already been installed more than 2 million times, according to estimates from app analytics company Sensor Tower.

Still, the app has already been the subject of some backlash, with more users deleting their accounts almost as quickly as they created them.

Now, the app has to not only fix the ingoing technical issues but persuade its new users to stick around long enough to pay for the service.