Here is promised Symform support?

I have no idea if there is still development going on at SYMFORM on this. I suggest you post your question in the SYMFORM community forum, and see what they say.

I saw the article you linked to before, and in fact it doesn't promise OS6 support.

It was mostly about the OS6 launch (dated 13 March 2013, when OS6 platforms became generally available), but then shifted to the now-discontinued genie marketplace:[quote="https://www.readynas.com/index.php?s=SYMFORM":10f31xkb]...Pahnke added, “We want to give our customers productivity-enhancing, innovative, and entertaining ways to do more with their NAS than they ever thought possible. With this in mind, ReadyNAS devices feature a rich set of embedded apps in addition to the growing library of add-ons found in the genie+ marketplace (genie.netgear.com/).”

Launched last year, genie+ marketplace is a platform for third party developers to deliver exciting, new applications which can be installed on ReadyNAS boxes with a single click. The suite of new applications includes productivity tools, media sharing applications, and a variety of other useful apps. Along with the currently available apps, NETGEAR has over 600 developers registered to create additional apps supporting the products announced today. Among the 40+ applications available are the Polkast media sharing application that allows owners to enjoy all of the content stored on their device from their mobile devices, the QNext FB social cloud application that enables users to share any of their content with any Facebook friend without having to upload the content, and the Symform Cloud Backup application that enables free online cloud backup...[/quote:10f31xkb].

The genie+ marketplace wasn't just for OS6 readynas, the vision was clearly to cover all netgear devices (routers, gateways and readynas at least). Looking at the original launch for the marketplace:[quote="http://www.netgear.com/about/press-releases/2012/10012012-javaone.aspx":10f31xkb]...Standards-based tools for developers
Whether developers are looking to create simple web apps, drivers or integration software for NETGEAR consumer devices, the NETGEAR Smart Network development platform simplifies the job. Complete, easy-to-access resources are available, including:
...
Java bundles: For apps hosted inside the home on NETGEAR always-on routers, gateways or ReadyNAS® devices, developers writing in Java are supplied with libraries, tutorials, sample applications and templates.[/quote:10f31xkb]

So the press release you cite doesn't actually doesn't promise SYMFORM support for OS6 (though it is easy to misread it to say that). But the community forum for SYMFORM suggests that SYMFORM was and perhaps still are working on it.