Vember Audio tells us that, as of 21th September 2018, Surge stopped being a commerical product and became an open-source project released under the GNU GPL v3 license. They say that, for the existing users, this will allow the community to make sure that it remains compatible as plug-in standards and Operating Systems evolve and, for everyone else, it is an exiting new free synth to use, hack, port, improve or do whatever you want with.
Vember Audio describe Surge thus,
A digital recording is just a sequence of numbers. Easily quantifiable as ones and zeros, stored on physical media, combined together into larger numbers to form a continuous stream of data.
Until you listen to it. Then it becomes real.
Surge is an instrument capable of generating truly beautiful sequences of numbers. Your ears will agree with us.
Architecturally speaking, Surge is a rather complex synthesizer. But because of how it's put together it's still easy to learn. Once you do, you will turn the sounds in your head to audio faster than ever.
The effortless workflow, attention to detail and the sound quality can't really be appreciated without trying it yourself.
Pricing and Availability: