Sorry about the 1.5-day silence, work plus sniffles kept me on all pistons. Updates coming!
Thanks for the comprehensively thought out discussion. I hear the inner GMs all trying to make sense of SR lore and background, something I've tried to grapple with over the years and editions. Here's my take, using just the 6e, and then referring to earlier ones if necessary for inspiration or guidance. (Which has been my original premise for starting this game in the first place).
We know there's no translation software in the 6e. And also none I can find in the earlier editions. This can mean it doesn't exist, or interestingly it may mean, using what Falconloft quoted above, have it transcribed to German, that we can get texts transcribed from one language to another. This still doesn't mean it is a basic programme installed in everyone's commlink; it sounds like a service we can employ someone to do. Now I know the non-existence of translation software is very strange, given that there are so many other sci-fi / futurist advances this game uses, but hold off for a bit, we'll reconcile this later.
Let me talk about Dejoker's proposal to invent an equivalent minor software to linguasoft, using the parallel of datasoft vis-a-vis knowsoft. I'll explain datasoft vs knowsoft again. A datasoft is a very small database of knowledge than a knowsoft. The examples given describe it as knowing one specific gang vs all the gangs in Seattle, or akin to one book vs a shelf/section of the library.
If we want to invent / house rule a langsoft (made up a new word for convenience) vis-a-vis linguasoft, I'd recommend using the same principles. Firstly, all skillsofts are level 1 to 6 only. No level 7. Secondly, linguasofts only go up to to skill level 4, so a langsoft cannot be higher. To clarify, linguasoft level 4 means you understand and speak exactly with the same proficiency as a native speaker would. Nothing illogical there. Eg, if you own many linguasofts, you would be understanding and speaking at native level proficiency in all of them. Level 1 means you gain the ability to use Perception tests to understand things in that language, which you could not have done before, p99. At level 4 you never have to roll. Note especially it still doesn't say you get the ability to translate! What this simply means is if your character who knows English as a native langauge, and has a linguasoft of level 4 Sperethiel, in total your character knows two languages, English and Sperethiel at a native level. I'll repeat, a linguasoft isn't a translation software.
Back to inventing a langsoft. A langsoft would be a small subset of a linguasoft (like a datasoft is a small subset of a knowsoft). I proposed earlier that this means a Japanese langsoft would be a specific language area of a Japanese linguasoft, eg business Japanese, or underworld Japanese, or scientific Japanese. (Other real world equivalents would be like legalese, or Cockney slang, or thieves' cant). Having a level 1 Cockney langsoft installed in your commlink allows you to process Cockney, at level 4 your commlink is able to process Cockney at a native level. It's a commlink programme, so unlike a skilljack interface, you don't actually possess the ability to speak it, you'll additionally need a direct neural interface, trodes, or some such. This bears repeating, to use the skill, you need a skilljack, and languages in this game are defined as skills.
So with this, I can get back to translation, the difficulties of which Falconloft tried to expound on earlier. To translate, you need to possess the language skills of two languages, eg. you know English, and you have a linguasoft that lets you know Japanese. If you know both, you can translate. But if you only can afford a Japanese langsoft for Japanese Yakuza slang in your commlink, when you use the commlink it will allow you to understand what these slang terms mean. Kinda like a dictionary, not so much a translator.
Alrighty, gonna have to crash for a bit, then new posts for everyone after that! Thanks for the patience!
Edit: I forgot to take into account one more consideration. Commlinks run software of these types: datasofts, mapsofts, shopsofts, tutorsofts. All these software aren't 'skills', mechanically they have no skill levels, mapsofts and shopsofts give a +1 dice pool modifier. So if we were to invent a langsoft which can be used in a commlink, it would not have skill levels either. Note the sentence above I deleted. A Cockney langsoft will enable a user to understand Cockney slang, ie. mechanically allow a Perception test to recognise and understand Cockney, just like a Pullayup gangs datasoft is a small subset of the Seattle gangs knowsoft, ie. mechanically allow a test of some sort on Pullayup gangs only.