[kenrose]

If it’s one you build yourself (e.g. Raspberry Pi with Kodi), it will be.

[kccqzy]

That's by definition not a third party box any more.

[allannienhuis]

Isn't it third party from the tv vendor? I think that was the implied context. Although If you consider yourself as the vendor who built the device (did you really?) that would be first-party I guess.