Here is an idea that could see RHP becoming multilingual within a matter of months:
The entire set of English phrases used in RHP would be compiled into its own section on the site.
Volunteers would select and translate phrases into their own language as time permitted. This would be achieved by clicking on a phrase, selecting the target language and entering its translation. Counters would indicate how many times a phrase had been translated into a given language. Once a phrase had been translated a certain number of times, that phrase would become locked for that language, and no further translations would be accepted. If all translations for a given phrase for a given language were identical, then that translation could be trusted.
I recommend setting this counter value greater than 1 to avoid bogus translations.
Once the entire set of translations was aquired for a given language, then that language would become available on RHP. Users could then select that language and RHP would display in the language.
I expect that even the chess notation used would need to be translated. The K, Q, R, B, N used in the notation would require translation.