There are already 11 certified Java EE 6 servers. It is actually amazing--Java EE 6 was released in 10 Dec, 2009. So we get almost every other month a new Java EE 6 server released. But: there are also servers available like Siwpas which are not certified, but are also working well (at least do not smoke after booting).
I smoke-tested some of them:
Web Apps, SPA, PWA with vanilla Java Script (ES 6+), CSS 3 and WebStandards only. As simple as possible, but not simpler. See you at: (Progressive) Web apps, Single Page Apps and WebStandards airhacks workshops at MUC airport, Winter Edition
airhacks.fm the podcast:
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