It is simultaneously possible that Ericsson banned Erlang in 1998 (a statement claimed multiple times by the creators of Erlang) and that Ericsson rescinded the ban later in 2004, when they hired back Joe Armstrong.
It's not false, Erlang was indeed banned at Ericsson, which caused Joe Armstrong to leave. They later reversed course and brought him, together with the language back. This is a well documented fact in the history of the language.
Just when we thought everything was going well, in 1998, Erlang
was banned within Ericsson Radio AB (ERA) for new product
development. This ban was the second most significant event in
the history of Erlang: It led indirectly to Open Source Erlang and
was the main reason why Erlang started spreading outside Ericsson.
The reason given for the ban was as follows:
The selection of an implementation language implies a more
long-term commitment than the selection of a processor and
OS, due to the longer life cycle of implemented products.
Use of a proprietary language implies a continued effort to
maintain and further develop the support and the development environment. It further implies that we cannot easily
benefit from, and find synergy with, the evolution following
the large scale deployment of globally used languages. [26]
quoted in [12].
In addition, projects that were already using Erlang were allowed to continue but had to make a plan as to how dependence upon Erlang could be eliminated. Although the ban was only within
ERA, the damage was done. The ban was supported by the Ericsson technical directorate and flying the Erlang flag was thereafter not favored by middle management."
And to be completely fair....
"6.2 Erlang in recent times
In the aftermath of the IT boom, several small companies formed during the boom have survived, and Erlang has successfully rerooted itself outside Ericsson. The ban at Ericsson has not succeeded in completely killing the language, but it has limited its
growth into new product areas.
The plans within Ericsson to wean existing projects off Erlang did not materialise and Erlang is slowly winning ground due to a form of software Darwinism. Erlang projects are being delivered on
time and within budget, and the managers of the Erlang projects are
reluctant to make any changes to functioning and tested software.
The usual survival strategy within Ericsson during this time
period was to call Erlang something else. Erlang had been banned
but OTP hadn’t. So for a while no new projects using Erlang were
started, but it was OK to use OTP. Then questions about OTP
were asked: “Isn’t OTP just a load of Erlang libraries?”—and so
it became “Engine,” and so on."
Around year 2008 being an Erlang coder was often more or less seen as being a COBOL coder in Sweden. Bluetail had sort of failed, having burned lots of VC, iirc.
So Erlang was something weird and custom that Ericsson used to build software for legacy phone exchanges. I remember that a colleague's wife working at Ericsson had received on-the-job training from essentially zero programming knowledge to become an Erlang developer in order to maintain some phone exchange software.
It's been fascinating to see it morph into something cool. Whatsapp, etc.
FWIW among PL nerds Erlang was "cool" in 2000 to 2007, too. It was constantly talked about on Lambda The Ultimate, I would have loved to have used it at my work at the time... I saw it used at multiple startups in the 2008-2010 period, and it eventually got deployed for the backend of Facebook's initial Messenger version, among other places.
If anything, it fell out of favour and lost hype wave for some time after that, while other languages copied aspects of the Actor model... and mostly the BEAM hype came back in the form of Elixir.
Yeah, I don't know why this falsehood continues to persist. WhatsApp and Ericsson engineers continue to work together to evolve Erlang, alongside a bunch of other people across the industry.
Not the original commenter, but from hearing Joe Armstrong speak on multiple occasions my recollection is that Erlang was blacklisted for some length of time (which allowed it to become an open source language), but eventually the company realized it still offered significant value.
False statement. Ericsson still uses Erlang, for example in their MME. Source: I used to work at Ericsson.