I'm editing my answer. I just checked the Samsung website and, I'm happy to say, they threw out all the junk.
They use to have a number of different, non-interchangeable, coding languages. And none of them really worked on the TV's of the other manufacturers either. This is most likely the reason why few applications were ever developed for those platforms.
Now they are supporting basic javascript. So, you have the opportunity to build yourself a TV web page and load it up as an application on Samsung and potentially run it from the Google-TV browser. However, I would verify whether your application requires specific HTML5 features (such as offline support) that may not be implemented in the Android-like browser version running on Google-TV. Having said that, you can always build an app that loads locally on Samsung and runs from a remote server on Google-TV?
... for some historical perspective on how we go to where we're at you can continue reading....
The implication of each manufacturer having their own unique OS creating developer fragmentation was probably predictable to them but they were likely working in a panic. After they became aware of the Apple TV when the first patents were make public in 2008 they understood the longer term impact if Apple provided hundred of thousand of applications worth of content and they had nothing to compete. So they got together and decided on a standard they would implement that would provide a non-fragmented solution allowing any app to run on the TV's of any supporting manufacturer. AKA: they got it right.
In 2009 a good number of them announced support for the Yahoo Connected TV standard. However, by 2010 the development framework, app store, etc that was promised had not materialized. This is likely when they all went in their own direction (although you can still buy Yahoo Connected TV sets from Samsung, Sony, LG, Vizio, and Panasonic today).
With the implementation of the Google-TV Market and the ability of developers to transition existing apps to Google-TV apps with only 20% or so of the effort of creating new (thus lowering the cost and supporting the business case for a TV version) that they have a solution that meets their original requirements.
Now, there's certainly going to be a little 'bitten once twice shy' coupled with revenue sharing discussions and perhaps the impact of Google being a hardware manufacturer (Motorola Mobility) but, at the end of the day, the inevitable is inevitable. They either take Google-TV or create their own, very close, must run existing applications, version of Android.
PS: I didn't look at the other manufacturers site.