"In February 1998, Ericsson Radio Systems banned the in-house use of Erlang for new products, citing a preference for non-proprietary languages. The ban caused Armstrong and others to make plans to leave Ericsson. In March 1998 Ericsson announced the AXD301 switch, containing over a million lines of Erlang and reported to achieve a high availability of nine "9"s. In December 1998, the implementation of Erlang was open-sourced and most of the Erlang team resigned to form a new company Bluetail AB. Ericsson eventually relaxed the ban and re-hired Armstrong in 2004."
Not wanting to rely on a fairly esoteric in-house language makes some sense.
Since then things have changed significantly of course.
There have been second hand report of the current leadership at Ericsson saying that opensourcing erlang was the worst decision they had taken. As it would have given way a massive competitive advantage.
Nearly 80% of OTP development is and has always been, done internally at Ericsson. And they barely use the libraries from the outside world. From inside Ericsson, erlang look a lot like a proprietary language
There's pros and cons to these kind of things. "Best tool for the job" reasoned purely from a technical point of view isn't necessarily the "best tool for the job" when everything is factored in.
It's hard for me to judge one way or the other; I wasn't at Ericsson in 1998, or indeed, ever at Ericsson. I just figured that the language wasn't open source at the time and that they came back on their decision just a few year later were important bits missing from the previous comment.
"In February 1998, Ericsson Radio Systems banned the in-house use of Erlang for new products, citing a preference for non-proprietary languages. The ban caused Armstrong and others to make plans to leave Ericsson. In March 1998 Ericsson announced the AXD301 switch, containing over a million lines of Erlang and reported to achieve a high availability of nine "9"s. In December 1998, the implementation of Erlang was open-sourced and most of the Erlang team resigned to form a new company Bluetail AB. Ericsson eventually relaxed the ban and re-hired Armstrong in 2004."
Not wanting to rely on a fairly esoteric in-house language makes some sense.
Since then things have changed significantly of course.